Seagrass related publications, 2011

Here's an unedited list of references (and abstracts where available) gleened from a quick keyword search for various seagrasses terms, hopefully useful in particular to those without easy access to online reference databases.

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Publications to date, 2011

Adachi, H., H. Yamano, T. Miyajima and M. Nakaoka (2010). "A simple and robust procedure for coring unconsolidated sediment in shallow water." Journal of Oceanography 66(6): 865-872. DOI: http://dx.doi.org/10.1007/s10872-010-0070-4
This article describes a simple, quick, and inexpensive procedure for coring unconsolidated sediment in shallow water (< 30 m from water surface). A similar to 1 m core is retrieved by a PVC pipe that penetrates sediment in response to the percussive force of a hand-operated hammering tool or air hammer. After retrieving the first core segment, a casing is inserted to allow access to deeper sediment layers. Pulverized sediment produced during coring is removed by a water-lubrication system that is powered by an electric pump attached to a generator. Using this system and procedure, five 2-m-long cores with excellent quality were retrieved.

Arceo-Carranza, D., M. E. Vega-Cendejas, J. L. Montero-Munoz and M. J. H. de Santillana (2010). "Influence of habitat type on diet fish associations in a tropical costal lagoon." Revista Mexicana De Biodiversidad 81(3): 823-837.
The abundance and turnover of fish species inhabiting Celestun lagoon were evaluated according to day-night cycles, as well as habitat type. Bimonthly sampling was done at 4 sites of the lagoon, 2 at the mouth and 2 at the inner zone. The sites for each zone include bottoms with and without submerged aquatic vegetation (VAS, FSV). At each site hydrologic parameters were registered to determine their relationship with fish community structure. Fish specimens were collected using a beach seine (15 x1.5 m, 2.5cm mesh) at day (10:00-13:00), twilight (18:0021:00) and night (02:00-05:00). Multivariate non-parametric (NPMANOVA, NMDS, betadisper) statistics were used for the analysis. Difference in fish species were found between habitats with VAS and FSV (F=2.6108, p=0.0114). The betadisper test indicated that species rate of replacement is low between habitats and during day-night cycles. Fish assemblages between habitats are more dynamic than day-night cycles, due to seagrass meadows that host great numbers of species providing protection and food availability.

Bricker, E., M. Waycott, A. Calladine and J. C. Zieman (2011). "High connectivity across environmental gradients and implications for phenotypic plasticity in a marine plant." Marine Ecology Progress Series 423: 57-67. DOI: http://dx.doi.org/10.3354/meps08962
Thalassia testudinum is prevalent throughout the western tropical Atlantic, Gulf of Mexico, and Florida. This seagrass inhabits a wide range of coastal ecosystems and published data suggest significant morphological variation in T. testudinum across acute physicochemical environmental gradients. Strong reliance on vegetative growth provokes expectations of a clonal signature in the population structure of this species. We utilize high resolution genetic data to explore the population structure of T. testudinum and evaluate the basis for this species’ plasticity as a function of a phenotypic versus a genotypic response. We studied one of the largest populations of T. testudinum, the Florida Bay system, and found that the population exhibited high levels of genetic diversity suggesting strong recruitment of sexually derived propagules. Allelic richness was high (ARIC = 5.94 to 7.33) and expected heterozygosity was consistently high across our study subpopulations (He = 0.558 to 0.673). There was no evidence of inbreeding within subpopulations (FIS = 0.02 to 0.13) and overall gene flow estimates were moderate to high (Nm = 5.71). These data support T. testudinum in Florida Bay as a single metapopulation with high genetic connectivity among subpopulations. Models of migration utilizing Bayesian modeling revealed a distinct directionality to immigration counter to models of historical formation of Florida Bay. We also found no evidence that meadows formed genetic subpopulations suggesting morphological variability observed across environmental gradients represents norms of reaction within the genetically diverse, interbreeding metapopulation. We suggest T. testudinum evolved phenotypic plasticity as a general purpose trait under natural selection.

Cengiz, S. and L. Cavas (2010). "A Promising Evaluation Method for Dead Leaves of Posidonia oceanica (L.) in the Adsorption of Methyl Violet." Marine Biotechnology 12(6): 728-736. DOI: http://dx.doi.org/10.1007/s10126-010-9260-8
Posidonia oceanica (Linnaeus) Delile is an endemic species in the Mediterranean Sea. In the present study, dead leaves of P. oceanica (L.) which are accumulated on the beach seasonally were used as an alternative low cost biosorbent to remove methyl violet (MV) from aqueous solution. In order to explain the adsorption kinetics, pseudo first-order and pseudo second-order kinetic models were investigated. It was obtained that the pseudo second-order model was well in line with our experimental results. Equilibrium data were analyzed according to Langmuir, Freundlich, and Dubinin-Radushkevich equations. Langmuir isotherm model corresponded well with equilibrium data than the others, and the maximum adsorption capacity of the biomass was found to be 119.05 mg g(-1) at 45A degrees C. Thermodynamic parameters, Delta GA degrees, Delta HA degrees, and Delta SA degrees, were calculated according to van't Hoff equation. Negative values of Gibbs free energy imply that the process is spontaneous. Consequently, dried biomass of this species can be an alternative and low cost material for the removal of MV from wastewaters. Moreover, since the remarkable adsorption capacity of these dead leaves compared to other low cost adsorbents has been observed, this beach waste could provide an economic contribution to the countries in the Mediterranean region.

Dethmers, K. E. M., M. P. Jensen, N. N. FitzSimmons, D. Broderick, C. J. Limpus and C. Moritz (2010). "Migration of green turtles (Chelonia mydas) from Australasian feeding grounds inferred from genetic analyses." Marine and Freshwater Research 61(12): 1376-1387. DOI: http://dx.doi.org/10.1071/mf10084
Coastal seagrass habitats in tropical and subtropical regions support aggregations of resident green turtles (Chelonia mydas) from several genetically distinct breeding populations. Migration of individuals to their respective dispersed breeding sites provides a complex pattern of migratory connectivity among nesting and feeding habitats of this species. An understanding of this pattern is important in regions where the persistence of populations is under threat from anthropogenic impacts. The present study uses mitochondrial DNA and mixed-stock analyses to assess the connectivity among seven feeding grounds across the north Australian coast and adjacent areas and 17 genetically distinct breeding populations from the Indo-Pacific region. It was hypothesised that large and geographically proximate breeding populations would dominate at nearby feeding grounds. As expected, each sampled feeding area appears to support multiple breeding populations, with two aggregations dominated by a local breeding population. Geographic distance between breeding and feeding habitat strongly influenced whether a breeding population contributed to a feeding ground (w(i) = 0.654); however, neither distance nor size of a breeding population was a good predictor of the extent of their contribution. The differential proportional contributions suggest the impact of anthropogenic mortality at feeding grounds should be assessed on a case-by-case basis.

Dijkstra, J. T. and R. E. Uittenbogaard (2010). "Modeling the interaction between flow and highly flexible aquatic vegetation." Water Resources Research 46. DOI: http://dx.doi.org/W1254710.1029/2010wr009246
Aquatic vegetation has an important role in estuaries and rivers by acting as bed stabilizer, filter, food source, and nursing area. However, macrophyte populations worldwide are under high anthropogenic pressure. Protection and restoration efforts will benefit from more insight into the interaction between vegetation, currents, waves, and sediment transport. Most aquatic plants are very flexible, implying that their shape and hence their drag and turbulence production depend on the flow conditions. We have developed a numerical simulation model that describes this dynamic interaction between very flexible vegetation and a time-varying flow, using the sea grass Zostera marina as an example. The model consists of two parts: an existing 1DV k-epsilon turbulence model simulating the flow combined with a new model simulating the bending of the plants, based on a force balance that takes account of both vegetation position and buoyancy. We validated this model using observations of positions of flexible plastic strips and of the forces they are subjected to, as well as hydrodynamic measurements. The model predicts important properties like the forces on plants, flow velocity profiles, and turbulence characteristics well. Although the validation data are limited, the results are sufficiently encouraging to consider our model to be of generic value in studying flow processes in fields of flexible vegetation.

Dissanayake, D. C. T. and G. Stefansson (2010). "Abundance and distribution of commercial sea cucumber species in the coastal waters of Sri Lanka." Aquatic Living Resources 23(3): 303-313. DOI: http://dx.doi.org/10.1051/alr/2010031
The sea cucumber stocks off the east and northwest coasts of Sri Lanka were estimated by surveying 1307 km(2) and 1779 km(2) by an underwater visual census (UVC) in June and October 2008 respectively. The presence of twenty-five sea cucumber species belonging to seven genera; Actinopyga, Bohadschia, Holothuria, Pearsonothuria, Stichopus, Thelenota and Acaudina was identified in five hundred sampling sites randomly selected in each area. The overall average density (+/- SD) of sea cucumbers was higher in the northwest (350 +/- 648 ind ha(-1)) than in the east (90 +/- 130 ind ha(-1)) and low-value species were predominant in both survey areas (79 +/- 125 ind ha(-1) in the east, 244 +/- 488 in the northwest) when compared with medium (10 +/- 34 ind ha(-1), 105 +/- 175 ind ha(-1), respectively) and high-value category (<2 ind ha(-1)). The estimated total biomass in the northwest (13 024 t) was roughly four times greater than the east (3027 t). Holothuria edulis was the most abundant species in numbers while Holothuria atra had the highest stock biomass in both areas. Sea cucumber densities were significantly different among the habitat (p < 0.001) and depth categories. The highest density was reported in rocky habitat associated with seagrass and / or macroalgae. The density of low-value species was significantly high in 1-10 m depth category (p < 0.001) in the northwest while other commercial groups were dominant in 20-30 m depth range in both areas. Temporal banning of the fishery for high and medium-value species would be a better management option to avoid further stock depletion.

Duarte, C. M., N. Marba, E. Gacia, J. W. Fourqurean, J. Beggins, C. Barron and E. T. Apostolaki (2010). "Seagrass community metabolism: Assessing the carbon sink capacity of seagrass meadows." Global Biogeochemical Cycles 24. DOI: http://dx.doi.org/Gb403210.1029/2010gb003793
The metabolic rates of seagrass communities were synthesized on the basis of a data set on seagrass community metabolism containing 403 individual estimates derived from a total of 155 different sites. Gross primary production (GPP) rates (mean +/- SE = 224.9 +/- 11.1 mmol O-2 m(-2) d(-1)) tended to be significantly higher than the corresponding respiration (R) rates (mean +/- SE = 187.6 +/- 10.1 mmol O-2 m(-2) d(-1)), indicating that seagrass meadows tend to be autotrophic ecosystems, reflected in a positive mean net community production (NCP 27.2 +/- 5.8 mmol O-2 m(-2) d(-1)) and a mean P/R ratio above 1 (1.55 +/- 0.13). Tropical seagrass meadows tended to support higher metabolic rates and somewhat lower NCP than temperate ones. The P/R ratio tended to increase with increasing GPP, exceeding, on average, the value of 1 indicative of metabolic balance for communities supporting a GPP greater than 186 mmol O-2 m(-2) d(-1), on average. The global NCP of seagrass meadows ranged (95% confidence limits of mean values) from 20.73 to 50.69 Tg C yr(-1) considering a low global seagrass area of 300,000 km(2) and 41.47 to 101.39 Tg C yr(-1) when a high estimate of global seagrass area of 600,000 km(2) was considered. The global loss of 29% of the seagrass area represents, therefore, a major loss of intense natural carbon sinks in the biosphere.

Farlin, J. P., L. S. Lewis, T. W. Anderson and C. T. Lai (2010). "Functional diversity in amphipods revealed by stable isotopes in an eelgrass ecosystem." Marine Ecology-Progress Series 420: 277-281. DOI: http://dx.doi.org/10.3354/meps08873
Amphipods are often dominant components of benthic marine communities and may exhibit taxon-specific differences in feeding behavior. As a result, variation in the composition of amphipod communities is an important metric for the interpretation of trophic dynamics in benthic marine ecosystems. Though previous studies of amphipod diets indicate functional diversity among taxa, few studies have examined whether these differences are detectible using time-integrated natural tracers of in situ feeding habits. We used stable isotope ratios of nitrogen (delta N-15) and carbon (delta C-13) to examine trophic structure among amphipod taxa belonging to 5 families in an eelgrass (Zostera marina) ecosystem in San Diego Bay, California. The relative contribution of sources of primary production to amphipod diets was further analyzed using a mixing model bracketed by 2 dominant sources of primary production in the system: eelgrass and algae. We detected significant differences in both delta C-13 and delta N-15 among amphipod taxa, indicating family-specific differences in feeding habits that generally agree with previous studies of amphipod diets. Hyalids fed almost exclusively on eelgrass, ischyrocerids and ampithoids tended to feed more on algae and eelgrass, respectively, and caprellids exhibited heterogeneous feeding on both algae and eelgrass. The relatively high delta N-15 value of oedicerotids suggested that this group was likely carnivorous. Our findings are in general agreement with previous descriptions of family-specific amphipod feeding behaviors, suggesting that stable isotopes are a useful tool for describing the functional roles of mesograzers in eelgrass ecosystems.

Ferraro, S. P. and F. A. Cole (2010). "Ecological periodic tables for nekton usage of four US Pacific Northwest estuarine habitats." Canadian Journal of Fisheries and Aquatic Sciences 67(12): 1957-1967. DOI: http://dx.doi.org/10.1139/f10-114
We compared the species composition and abundance of the total nekton community, using the Bray-Curtis similarity coefficient, and mean total nekton, fish and crab species richness, abundance and biomass, and shrimp abundance across four intertidal habitats in a US Pacific Northwest estuary: (i) eelgrass (Zostera marina); (ii) burrowing mud shrimp (Upogebia pugettensis); (iii) burrowing ghost shrimp (Neotrypaea californiensis); and (iv) unvegetated sand. Field sampling was conducted during daytime high tides, and was quantitative, stratified-by-habitat, randomized, and estuary-wide. More than 10 000 nekton specimens belonging to 64 taxa were collected in 454 samples during 10 sampling periods, each approximately one-month-long (from June to November), over 3 years (1998-2000). Non-metric multidimensional scaling analyses revealed annually recurring across-habitat patterns in total nekton Bray-Curtis similarity. Two-way (habitat, year) analyses of variance revealed annually recurring across-habitat patterns on 10 indicators of nekton-habitat quality and preference. Total nekton species richness, abundance, and biomass were, respectively, on average, 8 x, 25 x, and 25 x greater in eelgrass, 4 x, 6 x, and 5 x greater in mud shrimp, and 2 x, 3 x, and 2 x greater in ghost shrimp, than in sand habitat. Our findings validate the ecological relevance of our habitats to nekton, and suggest they can serve as elements in ecological periodic tables of nekton habitat usage.

Guidone, M., C. S. Thornber and E. Field (2010). "Snail grazing facilitates growth of a bloom-forming alga." Marine Ecology-Progress Series 420: 83-89. DOI: http://dx.doi.org/10.3354/meps08894
Herbivory often has a negative effect on plants. However, there is a growing number of examples, primarily in terrestrial ecosystems, where herbivory causes an increase in plant size, growth rate, and/or reproductive output. In marine ecosystems, the positive effects of herbivores on macroalgae are not as well studied, although limited evidence exists for herbivore-induced increases in macroalgal growth rates via 2 mechanisms: nutrient addition via grazer defecation, and epiphyte removal. In this study, we examined the effects of grazing by the mud snail Ilyanassa obsoleta on Ulva lactuca, the dominant bloom-forming macroalga in many New England estuaries. We found that the presence of I. obsoleta had a significant positive, rather than negative, effect on U. lactuca. Through caging experiments, we established that this positive effect was not due to fecal nutrient inputs from the snail. Similarly, snail contact in the absence of grazing did not affect U. lactuca growth rates. In contrast, grazing by I. obsoleta significantly reduced the microalgal cover on heavily fouled U. lactuca blades, indicating that snail herbivory of microalgal films likely facilitates U. lactuca growth. Our study demonstrates the surprising, positive effect that an abundant herbivore can have on the growth of a macroalgal bloom species.

Jung, C. A., S. E. Swearer and G. P. Jenkins (2010). "Changes in diversity in the fish assemblage of a southern Australian embayment: consistent spatial structuring at decadal scales." Marine and Freshwater Research 61(12): 1425-1434. DOI: http://dx.doi.org/10.1071/mf10080
Comprehensive assessment of spatio-temporal variation in assemblages, particularly relating to management and conservation efforts, should include examination of variation across scales. The present study investigated spatio-temporal variation at various scales in the fish fauna of Port Phillip, Australia, over 17 years. There were significant increases in diversity and changes in faunal composition in the most recent study, compared with 17 (+38%) and 7 (+151%) years ago. No significant year-to-year differences and no fortnightly differences within a season were found, supporting the notion of long-term changes. However, inter-seasonal variation was significant, with diversity highest in summer and lowest in winter (42.3% of summer diversity), illustrating substantial variation only at particular scales. The spatial structuring of assemblages was consistent at all temporal scales over 17 years. Fish assemblages and diversity varied significantly among sites and regions, but diversity was always highest on reefs in the eastern region of Port Phillip. However, the majority of spatial variation occurred among replicate transects (up to 75% of overall variation). Despite the high degree of small-scale spatio-temporal variability, the results provide evidence of long-term changes in faunal composition and diversity within the bay. Moreover, the results underline the necessity for multi-scalar approaches in ecological studies like abundance assessments.

Kalogirou, S., M. Corsini-Foka, A. Sioulas, H. Wennhage and L. Pihl (2010). "Diversity, structure and function of fish assemblages associated with Posidonia oceanica beds in an area of the eastern Mediterranean Sea and the role of non-indigenous species." Journal of Fish Biology 77(10): 2338-2357. DOI: http://dx.doi.org/10.1111/j.1095-8649.2010.02817.x
Temporal and spatial variation in density, biomass and body size of littoral fish species associated with nearshore Posidonia oceanica meadows was studied over an annual cycle in an area of the eastern Mediterranean Sea. A total of 109 350 littoral fishes were collected, belonging to 34 families and 88 species. Density of fishes peaked during the summer due to high numbers of juveniles. Season was a significant factor determining density, although number of species and biomass did not show any obvious seasonal pattern. Throughout the study, schooling planktivorous fish species such as the picarel Spicara smaris, the bogue Boops boops and the damselfish Chromis chromis were dominant, both in terms of density (80%) and biomass (70%). Temporal variation in density and body size of fishes was used to assess the seasonal and ontogenetic habitat use of each species, with their affinity to seagrass assessed by comparing their respective distribution on sand. Four functional guilds were created (juvenile migrants, seagrass residents, seasonal migrants and occasional visitors) to describe the habitat use of P. oceanica meadows by each species. Several species associated with P. oceanica meadows used this habitat mainly as juveniles during summer, although many others were present concurrently as adults and as juveniles. Among the species encountered, 11 were non-indigenous of Indo-Pacific origin, of which three used seagrasses mainly as juveniles and four as residents. The non-indigenous silverstripe blaasop Lagocephalus sceleratus ranked among the 10 most dominant species in terms of biomass (2%) and was classified as a seagrass resident.

Kannan, R. R. R., R. Arumugam and P. Anantharaman (2010). "Antibacterial potential of three seagrasses against human pathogens." Asian Pacific Journal of Tropical Medicine 3(11): 890-893. DOI: http://dx.doi.org/10.1016/s1995-7645(10)60214-3
Objective: To evaluate the antibacterial activity of Halophila stipulacea (H. stipulacea), Cymodocea serrulata (C. serrulata) and Halodule pinifolia (H. pinifolia) against seven human bacterial pathogens. Methods: The antibacterial activities of the extracts on the various test organisms using disc diffusion method and Minimum Inhibitory Concentraction (MIC). Results: Methanol and chloroform extracts of all the three seagrasses were active against all the tested pathogens, whereas the hexane extract of seagrasses was not active against Staphylococcus aureus (S. aureus). Antibacterial activity of three seagrass screened, was in the order of H. pinifolia > H. stipulacea > C. serrulata. Conclusions: This antibacterial studies can further investigated on seagrasses for purification of bioactive substance and its possible utility in disease control.

Kannan, R. R. R., R. Arumugam and P. Anantharaman (2010). "In vitro antioxidant activities of ethanol extract from Enhalus acoroides (LF) Royle." Asian Pacific Journal of Tropical Medicine 3(11): 898-901. DOI: http://dx.doi.org/10.1016/s1995-7645(10)60216-7
Objective:. To search for new sources of safe and inexpensive antioxidants, the leaf, root and rhizome of Enhalus acoroides (E. acoroides) were screened for the first time for their antioxidant activities. Methods: Samples of leaf, root and rhizome from E. acoroides were tested for total phenolic content, proanthocyanidins and in vitro antioxidant activity in terms of total antioxidant assay, DPPB assay and ERAP assay. Results: The leaf sample was found to have high levels of phenolic (0.323+/-0.028 mg TAE/g) and proanthocyanidins (0.570 0+/-0.000 3 mg TAE/g) when compared to root and rhizome. The leaf samples exhibited higher total antioxidant activity (11.770+/-0.026 mg Ascorbic acid equivalent/g), higher percentage of DPPH radical scavenging activity (25.76+/-0.04) and higher reducing power (18.060+/-0.073) in terms of mg GAE/g. In addition, there was a significant correlation between total phenolic content and total antioxidant activity (R-2=0.923), DPPH assay (R-2=0.509), FRAP assay (R-2=0.994). Similarly, significant correlation was found between the proanthocyanidin and total antioxidant activity (R-2=0.977), DPPH assay (R-2=0.464) and the FRAP assay (R-2=0.998). Conclusions: These results suggested that E. acoroides have strong antioxidant potential. Further study is necessary for isolation and characterization of the active antioxidant agents, which can be used to treat various oxidative stress related diseases.

Kennedy, H., J. Beggins, C. M. Duarte, J. W. Fourqurean, M. Holmer, N. Marba and J. J. Middelburg (2010). "Seagrass sediments as a global carbon sink: Isotopic constraints." Global Biogeochemical Cycles 24. DOI: http://dx.doi.org/Gb402610.1029/2010gb003848
Seagrass meadows are highly productive habitats found along many of the world's coastline, providing important services that support the overall functioning of the coastal zone. The organic carbon that accumulates in seagrass meadows is derived not only from seagrass production but from the trapping of other particles, as the seagrass canopies facilitate sedimentation and reduce resuspension. Here we provide a comprehensive synthesis of the available data to obtain a better understanding of the relative contribution of seagrass and other possible sources of organic matter that accumulate in the sediments of seagrass meadows. The data set includes 219 paired analyses of the carbon isotopic composition of seagrass leaves and sediments from 207 seagrass sites at 88 locations worldwide. Using a three source mixing model and literature values for putative sources, we calculate that the average proportional contribution of seagrass to the surface sediment organic carbon pool is similar to 50%. When using the best available estimates of carbon burial rates in seagrass meadows, our data indicate that between 41 and 66 gC m(-2) yr(-1) originates from seagrass production. Using our global average for allochthonous carbon trapped in seagrass sediments together with a recent estimate of global average net community production, we estimate that carbon burial in seagrass meadows is between 48 and 112 Tg yr(-1), showing that seagrass meadows are natural hot spots for carbon sequestration.

Kruschel, C. and S. Schultz (2010). "Lure-assisted visual census: a new method for quantifying fish abundance, behaviour, and predation risk in shallow coastal habitats." Marine and Freshwater Research 61(12): 1349-1359. DOI: http://dx.doi.org/10.1071/mf10042
Understanding the causes of variation in faunal abundance and diversity across shallow coastal habitats is a fundamental goal of marine ecology. Field methods for inferring a habitat effect on population density and predation risk are informative only if method biases are equal across habitats and species. We hypothesised that observation of fixed lures has a species by bias interaction if sampled species have different modes of predation, and that these biases are overcome by use of moving lures. We tested this hypothesis by observation of fixed and moving lures within seagrass and bare sediment in the Novigrad Sea, Croatian Adriatic. Both methods showed that ambush predators peaked in seagrass, wait-chasers peaked over bare sediment, and move-chasers were abundant in both. Stationary lures underestimated wait-chase and wait-ambush predators relative to moving lures, whereas moving lures did not underestimate the density of predators. These results indicate that stationary lures can underestimate both fish abundance and predation risk in the presence of waiting predators, and that if waiting predators are more abundant in structured habitat, then stationary lures will underestimate the predation risk within such habitats. Use of moving lures may be preferable for comparing habitats differing in structural complexity and frequency of predation modes.

Latimer, J. S. and S. A. Rego (2010). "Empirical relationship between eelgrass extent and predicted watershed-derived nitrogen loading for shallow New England estuaries." Estuarine Coastal and Shelf Science 90(4): 231-240. DOI: http://dx.doi.org/10.1016/j.ecss.2010.09.004
Seagrasses provide important ecological services that directly or indirectly benefit human well-being and the environment. Excess nitrogen inputs are a major cause of eelgrass loss in the marine environment. Here we describe the results of a study aimed at quantifying the extent of eelgrass as a function of predicted watershed-derived nitrogen loading for small-to-medium-sized shallow estuaries in New England. Findings confirm that reduced extent of eelgrass corresponds to increased loading of nitrogen to this class of estuary. At lower levels of nitrogen loading (<= 50 Kg ha(-1) yr(-1)), eelgrass extent is variable and is likely controlled by other ecosystem factors unrelated to water quality. At higher loading rates, eelgrass coverage decreases markedly, with essentially no eelgrass at loading levels >= 100 Kg ha(-1) yr(-1). Published by Elsevier Ltd.

Macquaker, J. H. S., M. A. Keller and S. J. Davies (2010). "Algal blooms and "marine snow": mechanisms that enhance preservation of organic carbon in ancient fine-grained sediments." Journal of Sedimentary Research 80(11-12): 934-942. DOI: http://dx.doi.org/10.2110/jsr.2010.085
Combined petrographic and geochemical methods are used to investigate the microfabrics present in thin sections prepared from representative organic carbon-rich mudstones collected from three successions (the Kimmeridge Clay Formation, the Jet Rock Member of the Whitby Mudstone Formation, and the pebble shale and Hue Shale). This study was initiated to determine how organic carbon-rich materials were being delivered to the sediment water interface, and what happened to them after deposition, prior to deep burial. Analyses of the fabrics present shows that they exhibit many common attributes. In particular they are all: (1) highly heterogeneous on the scale of a thin section, (2) organized into thin beds (< 10 mm thick) composed mainly of mineral mixtures of fine-grained siliciclastic detritus and carbonate materials, and (3) contain significant concentrations of organic carbon, much of which is organized into laminasets that contain abundant organomineralic aggregates and pellets. In addition, framboidal pyrite (range of sizes from < 20 mu m to < 1 mu m) and abundant agglutinated foraminifers are present in some units. The individual beds are commonly sharp-based and overlain by thin, silt lags. The tops of many of the beds have been homogenized and some regions of the pelleted laminasets contain small horizontal burrows. The organomineralic aggregates present in these mudstones are interpreted to be ancient examples of marine snow. This marine snow likely formed in the water column, particularly during phytoplankton blooms, and was then transported rapidly to the seafloor. The existence of the thin beds with homogenized tops and an in-situ infauna indicates that between blooms there was sufficient oxygen and time for a mixed layer to develop as a result of sediment colonization by diminutive organisms using either aerobic or dysaerobic metabolic pathways. These textures suggest that the constituents of these mudstones were delivered neither as a continuous rain of sediment nor were the bottom waters persistently anoxic. In addition, the presence of thin lags and sharp-based beds suggests that the seafloor was being episodically reworked during deposition. These fabrics indicate that conditions in the water columns and at the seafloors while these rocks were being deposited were very dynamic, and episodic fluxes of high concentrations of organic carbon to the seafloor, during phytoplankton blooms, likely enhanced preservation of organic carbon.

Maher, D. T. and B. D. Eyre (2010). "Benthic fluxes of dissolved organic carbon in three temperate Australian estuaries: Implications for global estimates of benthic DOC fluxes." Journal of Geophysical Research-Biogeosciences 115. DOI: http://dx.doi.org/G0403910.1029/2010jg001433
Light and dark benthic dissolved organic carbon (DOC) fluxes and sediment characteristics (total organic carbon (TOC), total nitrogen (TN), TOC isotope ratio (delta C-13), phospholipid fatty acid (PLFA) concentration, and compound-specific delta C-13) were measured seasonally in a range of habitats in three warm-temperate Australian estuaries to determine what factors control benthic DOC fluxes. Benthic DOC fluxes were seasonal with the highest rates generally observed during summer. Most habitats displayed uptake of DOC during the dark and efflux during the light, and were a net source of DOC to the overlying waters over the diel cycle. Macrophyte habitats (seagrass and macroalgae) had the highest benthic fluxes of DOC (up to similar to 50 mmol C m (2) d (1)). Organic matter supply to the sediment was dominated by in situ production, and both quantity and source exerted control over benthic DOC fluxes. DOC flux was tightly coupled to bacteria and algal PLFA concentrations during summer, and algal PLFA concentrations during winter, indicating a strong influence of microbial interactions on benthic DOC flux and a temperature-related decoupling of algae and bacteria under cooler conditions. Estimates of the global estuarine benthic DOC flux indicate that these areas are a significant source of DOC to the ocean (1-41 Tg C yr(-1)). Inclusion of macrophyte, salt marsh, mangrove, and intertidal benthic DOC flux estimates resulted in a higher global continental margin benthic DOC flux (106-416 Tg C yr(-1)) than the previous estimate (90 Tg C yr(-1)).

Mullarney, J. C. and S. M. Henderson (2010). "Wave-forced motion of submerged single-stem vegetation." Journal of Geophysical Research-Oceans 115. DOI: http://dx.doi.org/C1206110.1029/2010jc006448
We derive an analytical model for the wave-forced movement of single-stem vegetation and test the model against observed vegetation motion in a natural salt marsh. Solutions for constant diameter and tapered stems are expanded using normal mode solutions to the Euler-Bernoulli problem for a cantilevered beam. These solutions are compared with motion of water and of the sedge Schoenoplectus americanus observed (using synchronized current meters and video) in a shallow salt marsh (depth < 1 m). Consistent with theory, sedge motion led water motion, with the phase decreasing (from 90 to 0 degrees) with increasing wave frequency. After tuning of a single free parameter (Young's modulus), the theory successfully predicted the transfer function between measured water and stem motion. Formulae predicting frequency-dependent wave dissipation by flexible vegetation are derived. For the moderately flexible stems observed, the model predicted total dissipation was about 30% of the dissipation for equivalent rigid stems.

Santruckova, H., E. Rejmankova, B. Pivnickova and J. M. Snyder (2010). "Nutrient enrichment in tropical wetlands: shifts from autotrophic to heterotrophic nitrogen fixation." Biogeochemistry 101(1-3): 295-310. DOI: http://dx.doi.org/10.1007/s10533-010-9479-5
We used established long-term experimental P-amended plots in freshwater marshes of northern Belize to determine the impact of P input on nitrogen (N) fixation. Marshes with different conductivities and sulfate concentrations were selected to elucidate the effect of salinity and the contribution of sulfur reducing bacteria to the overall N fixation. Rates of N fixation in sediment, roots, and cyanobacterial mats was measured in laboratory incubation experiments (acetylene reduction assay calibrated by N-15(2) reduction assay) with and without the addition of sodium molybdate (sulfur reducing bacteria inhibitor). P has increased macrophyte primary production significantly, which led to the rapid elimination of cyanobacterial mats and the elimination of autotrophic N fixation. P addition enhanced heterotrophic N fixation in both the sediments and rhizosphere due primarily to increased C supply to the sediment. When expressed on a dry weight basis, root associated N fixation was higher than sediment N fixation, but the contribution of the root associated fixation to the total N fixation was small when expressed per square meter. Sulfur reducing bacteria were an important component of N fixation, contributing from 20 to 53% to the overall N fixation. A simple N budget was created to determine if N demands are met following P addition. The heterotrophic N fixation substituted in part for autotrophic cyanobacterial N fixation when P limitation was alleviated.

Siegal-Willott, J. L., K. Harr, L. A. C. Hayek, K. C. Scott, T. Gerlach, P. Sirois, M. Reuter, D. W. Crewz and R. C. Hill (2010). "Proximate Nutrient Analyses Of Four Species Of Submerged Aquatic Vegetation Consumed By Florida Manatee (Trichechus manatus latirostris) Compared To Romaine Lettuce (Lactuca sativa Var. longifolia)." Journal of Zoo and Wildlife Medicine 41(4): 594-602.
Free-ranging Florida manatees (Trichechus manatus latirostris) consume a variety of sea grasses and algae. This study compared the dry matter (DM) content, proximate nutrients (crude protein [CP], ether-extracted crude fat [EE], nonfiber carbohydrate [NFC], and ash), and the calculated digestible energy (DE) of sea grasses (Thalassia testudinum, Halodule wrightii, and Syringodium filiforme)collected in spring, summer, and winter, and an alga (Chara sp.) with those of romaine lettuce (Lactuca saliva var. longfolia). Neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and lignin (L) measured after ash-extraction were also compared. Results of statistical tests (alpha = 0.01) revealed DM content was higher in aquatic vegetation than in lettuce (P = 0.0001), but NDF and ADF were up to threefold greater, EE (P = 0.00001) and CP (P = 0.00001) were 2-9 times less, and NFC (P = 0.0001) was 2-6 times lower in sea grass than in lettuce, on a DM basis. Chara was lower in NDF, ADF, L, EE, CP, and NFC relative to lettuce on a DM basis. Ash content (DM basis) was higher (P = 0.0001), and DE was 2-6 times lower in aquatic vegetation than in lettuce. Sea grass rhizomes had lower L and higher ash contents (DM basis) than sea grass leaves. Based on the nutrient analyses, romaine lettuce and sea grasses are not equivalent forages, which suggests that the current diet of captive Florida manatees should be reassessed.

Sullivan, M. J. (2010). "Transfer of the benthic marine diatom Anaulus vallus to the genus Denticula." Vie Et Milieu-Life and Environment 60(2): 173-176.
Examination of type material of the marine diatom Anaulus vallus Nikolaev with scanning electron microscopy revealed that it possesses a canal raphe. The "pseudosepta" seen with light microscopy are actually fibulae. Based on this information, A. vallus has been transferred to the genus Denticula as Denticula vallus (Nikolaev) Sullivan. This species is morphologically quite similar to D. neritica Holmes & Croll but differs in its lack of longitudinal ribs parallel to the raphe sternum. The two taxa can not be distinguished under LM. Denticula vallus and D. neritica have been collected in abundance from seaweeds, seagrasses, and sea birds.

Taylor, S. L., M. J. Bishop, B. P. Kelaher and T. M. Glasby (2010). "Impacts of detritus from the invasive alga Caulerpa taxifolia on a soft sediment community." Marine Ecology-Progress Series 420: 73-81. DOI: http://dx.doi.org/10.3354/meps08903
Invasive primary producers can dramatically reorganize food webs through detrital subsidies. This study assessed (1) contributions of the invasive alga Caulerpa taxifolia to detrital resources of temperate Australian estuaries, and (2) effects of these contributions on sediment-dwelling invertebrates. In an invaded estuary, sampling of an intertidal shore indicated C. taxifolia fragments were consistently present in organic matter deposits and were particularly abundant following storms. Sampling of the alga across 6 invaded estuaries showed that the ratio of organic carbon to nitrogen (C:N) in fresh tissue varied between 7 and 16. To determine how C. taxifolia detritus influences benthic macrofaunal assemblages and whether this influence depends on the quantity and C:N ratio of C. taxifolia detritus, a manipulative field experiment was performed. On a sheltered intertidal mudflat, 0.25 m(2) plots of sediment were experimentally enriched with either a high (90 g DW) or low (30 g) loading of high C:N (14) or low C:N (7) C. taxifolia detritus. Experimental enrichment negatively affected the total abundance and species richness of macroinvertebrates relative to controls, and these effects increased with detrital loading. For some macrofauna, reducing the C:N ratio tended to exacerbate negative effects on abundances, whereas it moderated these effects for other species. Given that organic matter derived from invasive species can be transported beyond the distribution of live invaders, greater consideration should be given to the potential broad-scale effects of invasive primary producers on detrital pathways.

Chadlia, A. and M. M. Farouk (2011). "Rapid Homogeneous Esterification of Cellulose Extracted from Posidonia Induced by Microwave Irradiation." Journal of Applied Polymer Science 119(6): 3372-3381. DOI: http://dx.doi.org/10.1002/app.32973
In this article, we report on the synthesis of cellulose esters by the reaction of cellulose and some cyclic anhydrides, such as succinic, maleic, and phthalic anhydrides. For this, an esterification method was finalized. Indeed, cellulose extracted from Posidonia biomass was first solubilized in the solvent system lithium chloride (LiCl)/N,N-dimethylacetamide and then esterified by cyclic anhydride in the presence of catalysts such as N,N-dimethyl-4-aminopyridine, tripropylamine, tributylamine, and calcium carbonate. This method was fast and reproducible with the LiCl system as a solvent and with an efficient activation by controlled microwave power. In this way, the reaction time was reduced from several hours to just a few minutes. The reaction products were characterized by IR and solid-state cross-polarization/magic angle spinning C-13-NMR spectroscopy. The degree of substitution (DS) and the grafted ester group content of the different products were obtained by alkali saponification followed by titration of the excess alkali. Two activation methods were compared, and the results show that the application of classical heating gave less successful results than those obtained by microwave activation. Indeed, with microwave activation, a higher DS (2.25) was obtained after 10 min. However, with classical heating, a value of DS equal to 1.2 was obtained after 12 h. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3372-3381, 2011

Di Maida, G., A. Tomasello, F. Luzzu, A. Scannavino, M. Pirrotta, C. Orestano and S. Calvo (2011). "Discriminating between Posidonia oceanica meadows and sand substratum using multibeam sonar." Ices Journal of Marine Science 68(1): 12-19. DOI: http://dx.doi.org/10.1093/icesjms/fsq130
High-resolution, multibeam sonar (MBS) (455 kHz) was used to identify two typologies of seabed 8 m deep: Posidonia oceanica meadow and sandy substratum. The results showed that the heterogeneity of the architecture of the P. oceanica canopy and the relatively simple morphology of a sandy substratum can be detected easily by statistical indices such as standard deviation or range-of-beam depth. Based on these indices, an automated classification was performed for seabed mapping. The overall classification accuracy was as high as 99 and 98% in October and January, respectively. The probability that P. oceanica in situ was omitted on the map was < 7%, whereas the probability that an area classified as P. oceanica on the map did not correspond to the seagrass in situ was consistently negligible. Based on these results, high-resolution MBS can be considered to be an accurate tool for mapping P. oceanica and sand substrata, and its discriminating power seems to be independent of season (autumn or winter).

Earl, J., A. J. Fowler and S. Dittmann (2011). "Temporal variation in feeding behaviour and trophic ecology of the temperate hemiramphid, Hyporhamphus melanochir." Environmental Biology of Fishes 90(1): 71-83. DOI: http://dx.doi.org/10.1007/s10641-010-9719-5
The feeding ecology of southern garfish, Hyporhamphus melanochir, in South Australia was investigated to determine the dietary composition and diurnal feeding patterns, especially in relation to a hypothesised relationship between prey availability and feeding patterns. Samples of H. melanochir were collected at different times of the day and night during autumn and winter, and assigned to 3-hourly intervals. The dietary composition and feeding patterns were determined from gut contents analysis. The main food items were seagrasses (Zosteraceae) and hyperbenthic crustaceans, mainly amphipods. Polychaetes and insects were also consumed. A clear diurnal trophic shift was evident: seagrass was consumed in large volumes during the day, whilst hyperbenthic invertebrates dominated the diet during the night. Plankton samples indicated that this trophic shift reflected the higher abundances of hyperbenthic invertebrates in the water column at night. Less time was spent consuming seagrass during winter, coinciding with shorter day-lengths. H. melanochir has a strong trophic association with seagrass beds, which may account for the high garfish abundance in northern Gulf St. Vincent where extensive Zosteracean seagrass beds occur. This may be useful fundamental information for future environmentally-based fishery management decisions to help ensure the sustainability of southern garfish population and the ecosystem of which it is a part.

Espineira, J. M., E. N. Uzal, L. V. G. Ros, J. S. Carrion, F. Merino, A. R. Barcelo and F. Pomar (2011). "Distribution of lignin monomers and the evolution of lignification among lower plants." Plant Biology 13(1): 59-68. DOI: http://dx.doi.org/10.1111/j.1438-8677.2010.00345.x
Through application of chemical, biochemical and histochemical analyses, we provide new data on the absence/presence of syringyl lignins in the algal species Mastocarpus stellatus, Cystoseira baccata and Ulva rigida, the bryophytes Physcomitrella patens and Marchantia polymorpha, the lycophytes Selaginella martensii, Isoetes fluitans and Isoetes histrix, the sphenophyte Equisetum telmateia, the ferns Ceratopteris thalictroides, Ceratopteris cornuta, Pteridium aquilinum, Phyllitis scolopendrium and Dryopteris affinis, and the angiosperm Posidonia oceanica. Lignins, and especially syringyl lignins, are distributed from non-vascular basal land plants, such as liverworts, to lycopods and ferns. This distribution, along with the already reported presence of syringyl lignins in ginkgoopsids, suggests that syringyl lignin is a primitive character in land plant evolution. Here, we discuss whether the pathway for sinapyl alcohol recruitment was iterative during the evolution of land plants or, alternatively, was incorporated into the earliest land plants and subsequently repressed in several basal liverworts, lycopods, equisetopsids and ferns. This last hypothesis, which is supported by recent studies of transcriptional regulation of the biosynthesis of lignins, implies that lignification originated as a developmental enabler in the peripheral tissues of protracheophytes and would only later have been co-opted for the strengthening of tracheids in eutracheophytes.

Eyre, B. D., A. J. P. Ferguson, A. Webb, D. Maher and J. M. Oakes (2011). "Metabolism of different benthic habitats and their contribution to the carbon budget of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)." Biogeochemistry 102(1-3): 87-110. DOI: http://dx.doi.org/10.1007/s10533-010-9424-7
The major benthic habitats in a shallow oligotrophic sub-tropical coastal system were mapped, benthic productivity and respiration were measured seasonally (summer, winter) in each open water habitat, and an annual carbon budget was constructed using measured, modelled and literature fluxes to estimate the functional importance of each major benthic habitat to the whole ecosystem. Stable Zostera Seagrass Communities covered 16% of the open water system but made little contribution to whole system metabolism. In contrast, ephemeral Halophila Seagrass Communities covered only 8% of the open water system but contributed 46% of the net productivity (p). The less 'iconic' Inter- and Sub-tidal Pimpama Shoals also only had a small areal extent (10%) but accounted for 50% of the net benthic production. Similarly, Yabby Shoals only covered 27% of the open water system but accounted for 89% of the net respiration (r). Budget estimates suggest that lateral import of organic matter, most likely tidally transported phytoplankton trapped in seagrass beds, across the Broadwater boundaries was required to balance the carbon budget if any reasonable estimate of burial was invoked. However, budget errors make it difficult to distinguish this import from zero. This study demonstrated that shallow subtropical coastal systems have a complex mosaic of benthic habitats, and that some of the less 'iconic' habitats (i.e. non-seagrass, non-mangrove) also make an important functional contribution that controls the flow of energy and nutrients through the whole ecosystem and determines the net ecosystem metabolism and possible exchanges with adjacent systems.

Eyre, B. D., A. J. P. Ferguson, A. Webb, D. Maher and J. M. Oakes (2011). "Denitrification, N-fixation and nitrogen and phosphorus fluxes in different benthic habitats and their contribution to the nitrogen and phosphorus budgets of a shallow oligotrophic sub-tropical coastal system (southern Moreton Bay, Australia)." Biogeochemistry 102(1-3): 111-133. DOI: http://dx.doi.org/10.1007/s10533-010-9425-6
Denitrification, N-fixation, and dissolved inorganic and organic fluxes of nitrogen (N) and phosphorus (P) were measured in each of the major benthic habitat types of a shallow oligotrophic sub-tropical coastal system, and N and P budgets were constructed to quantify the importance of each habitat to N and P cycling in the whole ecosystem. The productivity/respiration (p/r) ratio (trophic status) of the habitats was an important control on the rates, direction (uptake, efflux) and composition (dissolved inorganic N (DIN), dissolved organic N (DON), N-2) of N fluxes across the sediment-water interface, with an efflux below p/r = 1.5 and an uptake above p/r = 1.5. The Zostera Seagrass Community was the most important habitat for N loss via net N-2 effluxes (denitrification; 48%). Denitrification rates in seagrass were higher than those previously measured in temperate regions, most likely due to greater availability of NH4 (+) for coupled nitrification-denitrification. Yabby Shoals (sub-tidal shoals inhabited by burrowing shrimp, Trypaea australiensis) accounted for the second largest loss of N via denitrification, the largest recycling of DIN and dissolved inorganic P (DIP; statistically significant only during the dark in summer) across the sediment-water interface and the second largest uptake of DON (statistically significant only in summer). This study highlighted that shallow subtropical coastal systems have a complex mosaic of benthic habitats and that some less 'iconic' habitats (i.e. non-seagrass) also make an important functional contribution that controls the flow of N and P through the whole ecosystem.

Grol, M. G. G., I. Nagelkerken, A. L. Rypel and C. A. Layman (2011). "Simple ecological trade-offs give rise to emergent cross-ecosystem distributions of a coral reef fish." Oecologia 165(1): 79-88. DOI: http://dx.doi.org/10.1007/s00442-010-1833-8
Ecosystems are intricately linked by the flow of organisms across their boundaries, and such connectivity can be essential to the structure and function of the linked ecosystems. For example, many coral reef fish populations are maintained by the movement of individuals from spatially segregated juvenile habitats (i.e., nurseries, such as mangroves and seagrass beds) to areas preferred by adults. It is presumed that nursery habitats provide for faster growth (higher food availability) and/or low predation risk for juveniles, but empirical data supporting this hypothesis is surprisingly lacking for coral reef fishes. Here, we investigate potential mechanisms (growth, predation risk, and reproductive investment) that give rise to the distribution patterns of a common Caribbean reef fish species, Haemulon flavolineatum (French grunt). Adults were primarily found on coral reefs, whereas juvenile fish only occurred in non-reef habitats. Contrary to our initial expectations, analysis of length-at-age revealed that growth rates were highest on coral reefs and not within nursery habitats. Survival rates in tethering trials were 0% for small juvenile fish transplanted to coral reefs and 24-47% in the nurseries. As fish grew, survival rates on coral reefs approached those in non-reef habitats (56 vs. 77-100%, respectively). As such, predation seems to be the primary factor driving across-ecosystem distributions of this fish, and thus the primary reason why mangrove and seagrass habitats function as nursery habitat. Identifying the mechanisms that lead to such distributions is critical to develop appropriate conservation initiatives, identify essential fish habitat, and predict impacts associated with environmental change.

Matich, P., M. R. Heithaus and C. A. Layman (2011). "Contrasting patterns of individual specialization and trophic coupling in two marine apex predators." Journal of Animal Ecology 80(1): 294-305. DOI: http://dx.doi.org/10.1111/j.1365-2656.2010.01753.x
1. Apex predators are often assumed to be dietary generalists and, by feeding on prey from multiple basal nutrient sources, serve to couple discrete food webs. But there is increasing evidence that individual level dietary specialization may be common in many species, and this has not been investigated for many marine apex predators. 2. Because of their position at or near the top of many marine food webs, and the possibility that they can affect populations of their prey and induce trophic cascades, it is important to understand patterns of dietary specialization in shark populations. 3. Stable isotope values from body tissues with different turnover rates were used to quantify patterns of individual specialization in two species of 'generalist' sharks (bull sharks, Carcharhinus leucas, and tiger sharks, Galeocerdo cuvier). 4. Despite wide population-level isotopic niche breadths in both species, isotopic values of individual tiger sharks varied across tissues with different turnover rates. The population niche breadth was explained mostly by variation within individuals suggesting tiger sharks are true generalists. In contrast, isotope values of individual bull sharks were stable through time and their wide population level niche breadth was explained by variation among specialist individuals. 5. Relative resource abundance and spatial variation in food-predation risk tradeoffs may explain the differences in patterns of specialization between shark species. 6. The differences in individual dietary specialization between tiger sharks and bull sharks results in different functional roles in coupling or compartmentalizing distinct food webs. 7. Individual specialization may be an important feature of trophic dynamics of highly mobile marine top predators and should be explicitly considered in studies of marine food webs and the ecological role of top predators.

Noel, L., C. Testu, C. Chafey, P. Velge and T. Guerin (2011). "Contamination levels for lead, cadmium and mercury in marine gastropods, echinoderms and tunicates." Food Control 22(3-4): 433-437. DOI: http://dx.doi.org/10.1016/j.foodcont.2010.09.021
As part of a specific monitoring programme, total lead (Pb), cadmium (Cd) and mercury (Hg) concentrations in marine gastropods (common winkle, common whelk, abalone and murex), echinoderms (purple sea urchin and black sea cucumber) and tunicates (an ascidian species) were investigated by the French National Reference Laboratory (NRL) for trace elements in foodstuffs of animal origin. These elements were analysed by atomic absorption spectrometry in order to evaluate the safety of these species for human consumption. The highest levels of Hg and Cd were found in murexes, 0.185 mg kg(-1) and 0.853 mg kg(-1), respectively; whereas the highest level of Pb was detected in ascidians (0.505 mg kg(-1)). Hg and Pb concentrations were always below the maximum levels set by the European legislation (0.5 mg Hg kg(-1) and 1.5 mg Pb kg(-1) wet mass) and for Cd, only 2 samples of murex.(2.09 +/- 0.42 rag kg(-1) and 2.33 +/- 0.46 mg kg(-1)) exceeded the maximum level set by French legislation of 2.0 mg kg(-1) wet mass. (C) 2010 Elsevier Ltd. All rights reserved.

Royo, C. L. Y., G. Pergent, T. Alcoverro, M. C. Buia, G. Casazza, B. Martinez-Crego, M. Perez, F. Silvestre and J. Romero (2011). "The seagrass Posidonia oceanica as indicator of coastal water quality: Experimental intercalibration of classification systems." Ecological Indicators 11(2): 557-563. DOI: http://dx.doi.org/10.1016/j.ecolind.2010.07.012
The pervasive use of ecological indices is increasingly requiring actions of harmonisation. Specifically, within the EU Water Framework Directive, an important effort in methods intercalibration is being done. However, a significant limitation in comparability assessment arises from the datasets used, which have different geographic origins. The purpose of our study was to perform an experimental intercalibration, where data were collected specifically on a set of common sites and following all the requirements of the methods being assessed. Three indices based on the marine angiosperm Posidonia oceanica, the POMI, the BiPo and the PoSte, were applied to sites in three different geographical areas of the western Mediterranean: Catalonia, Corsica and Southern Italy (Ischia), distant between hundreds and more than thousands of kilometers. Two indices, POMI and BiPo, showed not only a very good relationship with human pressures (measured on a common scale for all sites) but also a high comparability, in all aspects investigated. The differences found for the third one (PoSte) are hypothesised as being due to a different rationale used to define reference conditions, the different metrics used in the index, and in particular to a different definition of ecological status in relation to the time scale of the response to anthropogenic pressures. Our study demonstrates that indices with very different approaches can provide fully reliable and comparable results. (C) 2010 Elsevier Ltd. All rights reserved.

Thedinga, J. F., S. W. Johnson and A. D. Neff (2011). "Diel differences in fish assemblages in nearshore eelgrass and kelp habitats in Prince William Sound, Alaska." Environmental Biology of Fishes 90(1): 61-70. DOI: http://dx.doi.org/10.1007/s10641-010-9718-6
The importance of a particular habitat to nearshore fishes can be best assessed by both diurnal and nocturnal sampling. To determine diel differences in fish assemblages in nearshore eelgrass and understory kelp habitats, fishes were sampled diurnally and nocturnally at six locations in western Prince William Sound, Alaska, in summer 2007. Abundance of fish between day and night were similar, but species composition and mean size of some fish changed. Species richness and species diversity were similar in eelgrass during the day and night, whereas in kelp, species richness and species diversity were greater at night than during the day. In eelgrass, saffron cod (Eleginus gracilis) was the most abundant species during the day and night. In kelp, the most abundant species were Pacific herring (Clupea pallasii) during the day and saffron cod at night. Diel differences in fish size varied by species and habitat. Mean length of saffron cod was similar between day and night in eelgrass but was greatest during the day in kelp. Pacific herring were larger at night than during the day in kelp. Diel sampling is important to identity nearshore habitats essential to fish and help manage fish stocks at risk.