Diversity Of Benthic Communities Research Articles

Detecting baffle mudstones using microfossils: an integrated working example from the Cardamom Field, Block 427 Garden Banks, Gulf of Mexico

Sedimentological observations, planktonic microfossil data, terrigenous index proxy data, benthic morphogroup analyses, pressure analyses and geochemical fingerprinting were integrated in order to assess the nature of mudstones in the Cardamom Field in the Auger salt withdrawal minibasin (Gulf of Mexico). Both ponded and slope accommodation have occurred through the salt basin's history resulting in complex stratigraphic architecture of stacked submarine lobes and channels. Continuous core (164ft) from the Messinian reservoir unit enabled this study to assess the depositional nature of the mud-rich intervals. Four mudstone facies (Mudstones 1–4) and respective depositional settings were interpreted. A modified benthic foraminifera microfacies model, in conjunction with variations recorded in planktonic flora and fauna abundances and reworking, serves as the key reference for the paleoecological interpretations. Of particular interest is the potential of a 41ft thick (below seismic resolution) intra-reservoir mudstone (Mudstone 3) to act as a baffle/barrier to fluid flow between the lower U Sand and the upper U Sand. Mudstone 3 shows a hemipelagic character containing a diverse benthic community, high abundances of autochthonous planktonic flora and fauna, reduced terrigenous input and extensive bioturbation. Downhole formation pressure data and fluid fingerprinting from the reservoir pay sands (upper and lower U Sands) show significant differences in the calculated pressure gradients and fluid composition. This suggests that most likely the two reservoir pay sands are not in vertical communication. Mudstone 3 paleoenvironmental analyses suggest the lateral extension of a possible baffle/barrier to vertical fluid flow. These results show that benthic morphogroup analyses in mudstones can be a robust method to assess reservoir compartmentalization and consequently, impact field development planning and reservoir modeling.

Trophic Ecology of Breeding White-Headed Steamer-Duck (Tachyeres leucocephalus)

Abstract. White-headed Steamer-Ducks (Tachyeres leucocephalus) are flightless waterfowl endemic to a small section of coastline in Patagonia, Argentina. This study provides the first detailed information on White-headed Steamer-Duck diet composition, foraging behavior and prey availability. This study was conducted in the northern San Jorge Gulf, Patagonia, during 2007. Fifteen feeding territories were identified, and food availability was quantified within them and also within unused areas. A total of 45 feces were analyzed to determine diet composition, and foraging behaviors of females were monitored. Benthic community diversity differed between territories and non-territories. Overall, diversity and invertebrate abundance tended to be higher in territories. Ten invertebrate prey taxa were identified in adult diets, and the most frequent prey in feces were crabs, mussels, and ragworms. Head-neck dipping was the most common method of feeding. Our results improve the understanding of the relationship bet...

Assembleia de ermitões nas proximidades de ilhas costeiras do sudeste do Brasil

An assortment of environmental factors may limit the permanence of hermit crabs in the environment, and determination of certain ecological indices can reveal the current conditions of the assemblage. This study evaluated the assemblage of hermit crabs near two islands adjacent to areas with fishing activity. Hermit crabs were collected monthly near Couves and Mar Virado islands on the southeastern coast of Brazil, from January through December 1998. Environmental factors were also recorded monthly. Ecological indices including species richness, diversity, evenness and dominance were calculated. The environmental characteristics differed between the islands, which helps to explain the differences in the composition of hermit crabs between the locations. Hermit crabs were significantly more abundant near Couves Island, where, according to the canonical correspondence analysis (CCA), the environmental parameters varied less. The Monte Carlo test (P < 0.05) confirmed the CCA model, indicating a strong correlation between the species of hermit crabs, bottom and surface water temperatures, and sediment organic-matter content. The presence of ovigerous females throughout the year indicates that these areas are favorable for reproduction. These results indicate that the environmental heterogeneity allows the establishment of different species of hermit crabs, influencing species richness and abundance of individuals in the ecosystem. These conditions favor the establishment of diverse benthic communities near the studied islands. Keywords : Diogenidae, Paguridae, diversity, abundance, multivariate analysis, Dardanus insignis, Loxopagurus loxochelis .

Widespread overspill from a saline density‐current channel and its interaction with topography on the south‐west Black Sea shelf

AbstractSeaward of the Bosphorus Strait, the south‐west Black Sea shelf is dominated by the world's largest channel network maintained by a quasi‐continuous saline (ca 35 → 31 psu) underflow. Calculations indicate that &gt;85% of the initial discharge of ca 104 m3s−1 spills overbank before the shelf edge. This paper documents interaction of the overspill with sea bed topography using multibeam bathymetry, echo‐sounder images of the water column, conductivity–temperature–depth profiles and sediment cores. Overbank spill is widespread, particularly through crevasse channels and on the middle shelf where confinement by channel banks is negligible. Towards the outer shelf, the wind‐driven Rim Current advects mud along the shelf, contributing to levée successions and deposition on stoss sides of elongate transverse ridges. Echo‐sounder profiles reveal metre‐scale eddies over megaflutes, and breaking lee waves and internal hydraulic jumps over ridges. Megaflutes reach 600 m long and 7 m deep, yet form where the underflow, outside the flute, is no thicker than ca 2 to 5 m. Two types of elongate seaward‐facing ridges are recognized. Type 1 ridges, 2 to 5 m high, consist of bivalve‐rich muddy sand in low‐angle (3·5° to 6°) cross‐sets created by the underflow. Type 2 ridges, ca 5 m high, have crests up to 2 km long and a buried wedge‐shaped foundation (the ‘ridge‐core’) comprised of facies similar to Type 1 ridges. These ridge‐cores are blanketed on the landward side by stratified muds, and are capped by obliquely oriented ribs supporting a diverse benthic community. This facies distribution is interpreted to result from stoss‐side and lee‐side velocity and turbulence fluctuations induced by internal hydraulic jumps and breaking lee waves in overspilling portions of the underflow. Experimental results published by W.H. Snyder and co‐workers effectively explain ridge evolution and flow across the ridges, and therefore can be applied with confidence to less easily studied deep‐marine settings swept by turbidity currents.

The effects of spatial and temporal variability at the sediment surface on aquatic eddy correlation flux measurements

The eddy correlation technique has become a widely used approach to measure ecosystem scale fluxes in aquatic benthic environments; however, there are few theoretical studies designed to guide deployment planning, the characterization of flux variability, or how to correctly interpret measured fluxes. Here, a three‐dimensional numerical model for the turbulent transport and mixing in the near‐bottom water was used to examine how well variations in vertical flux due to heterogeneities in the benthic community are integrated in eddy correlation measurements. The results showed that an appropriate choice of measuring height above the sediment surface is crucial to obtain an accurate average of the vertical flux from heterogeneous benthic communities. Through regression analysis of modeling results, a set of simple analytical expressions were derived for this threshold measuring height as a function of two parameters: heterogeneity patch size and sediment surface roughness. The same model was also used to examine the time lag between when a change in vertical flux occurs at the sediment surface and when it reaches the measuring point. The results showed that this response time varies by several orders of magnitude depending on flow velocity, sediment surface roughness, and measuring height. Simple analytical expressions were also derived for the response time. Overall, the findings indicate that both the spatial variability in benthic communities and the response to temporal changes are important factors that should be considered in planning eddy correlation measurements and interpreting eddy correlation fluxes.

Gaining Ground—Cleaning with Mesenterial Filaments by the Cold-Water Coral &lt;I&gt;Desmophyllum Dianthus?&lt;/I&gt;

The solitary cosmopolitan cold-water coral Desmophyllum dianthus (Esper, 1794) (A, scale bar approximately 1 cm) occurs as a deep-water emergent species in Patagonian fjords, Chile, and can form extensive banks (Forsterra et al. 2005). This coral functions as a bioengineer by providing a 3D habitat for a diverse benthic community (Forsterra et al. 2005). With skeletal growth, the living tissue is retracted by the organism to the upper part of the calyx, leaving the lower skeleton uncovered. Endolithic algae are then able to enter the tissue covered skeleton from below and start to encrust the tissue covered part of the skeleton (Forsterra et al. 2005, 2008). They are visible as a greenish coat on the skeleton (A). The algae are able to bore into the skeleton (Forsterra et al. 2005) and thus could interfere with the coral’s calcifying process. This process could result in a parasitic behavior (Forsterra et al. 2012) rather than the previously hypothesized (Forsterra and Haussermann 2008) symbiotic or even mutualistic relationship. This infection by algae may be the primary reason for the peculiar behavior we observed on several specimens both in situ (A) and in our aquaria system (B–D, scale bar approximately 1 cm). After an acclimatization time in our aquaria system, wild collected corals were well adapted and well fed, and secondarily expanded their tissue toward their lower skeleton (about 1 cm in 4 mo, CJ and GMS pers obs), recovering an area that had been without any tissue. Concomitantly, the corals everted their mesenterial filaments between this re-entered outer-skeleton and the covering tissue layer (A, B; C, D: both enlargements of B). During the eversion of the mesenterial filaments the new tissue generally appeared unusually pleated (C, D) in contrast to a less common smooth tissue surface (A). This was not a short-term or rare mechanism: corals maintained this behavior in the aquaria over multiple months. Several tropical coral species are known to eject their mesenterial filaments to digest prey too large to be swallowed (Yonge 1930). The tropical, branching coral Acropora pulchra (Brook, 1891) has even been observed to clean the substrate before it expands its tissue and skeleton (Roff et al. 2008). Our preliminary observations suggest a combination of both mechanisms in this cold-water coral. Mesenterial filaments could be digesting the growing algae below their tissue, but also may be cleaning the substrate (their own skeleton) prior to further tissue expansion.

A Three Year Assessment of the Influence of Physical Habitat, Pyrethroids and Metals on Benthic Communities in Two Urban Calfornia Streams

This three year study was designed to characterize benthic communities (macroinvertebrates) and physical habitat annually in two urban stream areas (Arcade Creek and Salinas streams) in California. Concurrent water quality evaluations, physical sediment parameters, pyrethroids, and bulk metals [including simultaneously extracted metals (SEM) and acid volatile sulfides (AVS) ratios] were also measured in both study areas. The relationship of various benthic metrics to physical habitat metrics, pyrethroids, and metals was evaluated for the the three year data set (2009 -2011) using univariate analysis, stepwise multiple regression analysis and canonical correlation analysis. Habitat conditions were determined to be poor in Arcade Creek and extremely poor in the Salinas streams. Tolerant benthic taxa were dominant in both study areas but degraded communities more apparent in Salinas streams. Canonical correlation analysis of the three year data set for Arcade Creek indicated that, while benthic community diversity was inversely related to toxicants (metals and pyrethroids) in the sediments, community composition appeared to be more closely related to physical habitat quality. The statistical analyses conducted on the three year data set from Salinas streams detected fewer and weaker relationships between benthic metrics and environmental variables than did the analyses of data from Arcade Creek, likely due to the greater degree of overall environmental degradation of the Salinas streams. However, habitat (particularly sediment deposition) appeared to be the most significant stressor. In summary the tthree year data sets for both streams showed more significant relationships with benthic metrics and habitat metrics than with pyrethroid or metals.

HYDRODYNAMICS OF THE CONDADO LAGOON

HYDRODYNAMICS OF THE CONDADO LAGOON

Variation in benthic communities of eastern Caribbean coral reefs in relation to surface sediment composition

The effects of sedimentation on coral reefs are commonly studied at local scales, but larger-scale patterns have been elusive, making it difficult to determine the role of sedimentation in region-wide changes in these ecosystems. We examined the relationships between characteristics of reef-associated surface sediment and benthic composition of 22 reefs around 11 islands of the eastern Caribbean. The terrigenous fraction in surface sediment increased with proximity to a clear source of sediment input. The percent cover of live coral, macroalgae, and turf algae decreased with higher terrigenous sediment fraction, while sponge cover increased. Sites with sediment containing high and low terrigenous fraction differed in coral species assemblages. In particular, the cover of Montastraea annularis complex decreased with increasing terrigenous sediment fraction. The proportion of fine-grained sediment had no effect on benthic composition. These results suggest that sedimentation may play a role in shaping coral reef communities at a regional scale.

Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 464:89-105 (2012) - DOI: https://doi.org/10.3354/meps09892 Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels Laurie C. Hofmann*, Sandra Straub, Kai Bischof Marine Botany, Bremen Marine Ecology Center for Research and Education, University of Bremen, Leobener Straße NW2, 28359 Bremen, Germany *Email: l.hofmann@uni-bremen.de ABSTRACT: Since pre-industrial times, uptake of anthropogenic CO2 by surface ocean waters has caused a documented change of 0.1 pH units. Calcifying organisms are sensitive to elevated CO2 concentrations due to their calcium carbonate skeletons. In temperate rocky intertidal environments, calcifying and noncalcifying macroalgae make up diverse benthic photoautotrophic communities. These communities may change as calcifiers and noncalcifiers respond differently to rising CO2 concentrations. In order to test this hypothesis, we conducted an 86 d mesocosm experiment to investigate the physiological and competitive responses of calcifying and noncalcifying temperate marine macroalgae to 385, 665, and 1486 µatm CO2. We focused on comparing 2 abundant red algae in the Northeast Atlantic: Corallina officinalis (calcifying) and Chondrus crispus (noncalcifying). We found an interactive effect of CO2 concentration and exposure time on growth rates of C. officinalis, and total protein and carbohydrate concentrations in both species. Photosynthetic rates did not show a strong response. Calcification in C. officinalis showed a parabolic response, while skeletal inorganic carbon decreased with increasing CO2. Community structure changed, as Chondrus crispus cover increased in all treatments, while C. officinalis cover decreased in both elevated-CO2 treatments. Photochemical parameters of other species are also presented. Our results suggest that CO2 will alter the competitive strengths of calcifying and noncalcifying temperate benthic macroalgae, resulting in different community structures, unless these species are able to adapt at a rate similar to or faster than the current rate of increasing sea-surface CO2 concentrations. KEY WORDS: Competition · Corallina officinalis · Chondrus crispus · Calcification · Ocean acidification · Mesocosm Full text in pdf format PreviousNextCite this article as: Hofmann LC, Straub S, Bischof K (2012) Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels. Mar Ecol Prog Ser 464:89-105. https://doi.org/10.3354/meps09892 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 464. Online publication date: September 19, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

The Influence of Coral Reef Benthic Condition on Associated Fish Assemblages

Accumulative disturbances can erode a coral reef’s resilience, often leading to replacement of scleractinian corals by macroalgae or other non-coral organisms. These degraded reef systems have been mostly described based on changes in the composition of the reef benthos, and there is little understanding of how such changes are influenced by, and in turn influence, other components of the reef ecosystem. This study investigated the spatial variation in benthic communities on fringing reefs around the inner Seychelles islands. Specifically, relationships between benthic composition and the underlying substrata, as well as the associated fish assemblages were assessed. High variability in benthic composition was found among reefs, with a gradient from high coral cover (up to 58%) and high structural complexity to high macroalgae cover (up to 95%) and low structural complexity at the extremes. This gradient was associated with declining species richness of fishes, reduced diversity of fish functional groups, and lower abundance of corallivorous fishes. There were no reciprocal increases in herbivorous fish abundances, and relationships with other fish functional groups and total fish abundance were weak. Reefs grouping at the extremes of complex coral habitats or low-complexity macroalgal habitats displayed markedly different fish communities, with only two species of benthic invertebrate feeding fishes in greater abundance in the macroalgal habitat. These results have negative implications for the continuation of many coral reef ecosystem processes and services if more reefs shift to extreme degraded conditions dominated by macroalgae.

Authigenic carbonates from active methane seeps offshore southwest Africa

The southwest African continental margin is well known for occurrences of active methane-rich fluid seeps associated with seafloor pockmarks at water depths ranging broadly from the shelf to the deep basins, as well as with high gas flares in the water column, gas hydrate accumulations, diagenetic carbonate crusts and highly diverse benthic faunal communities. During the M76/3a expedition of R/V METEOR in 2008, gravity cores recovered abundant authigenic carbonate concretions from three known pockmark sites—Hydrate Hole, Worm Hole, the Regab pockmark—and two sites newly discovered during that cruise, the so-called Deep Hole and Baboon Cluster. The carbonate concretions were commonly associated with seep-benthic macrofauna and occurred within sediments bearing shallow gas hydrates. This study presents selected results from a comprehensive analysis of the mineralogy and isotope geochemistry of diagenetic carbonates sampled at these five pockmark sites. The oxygen isotope stratigraphy obtained from three cores of 2–5 m length indicates a maximum age of about 60,000–80,000 years for these sediments. The authigenic carbonates comprise mostly magnesian calcite and aragonite, associated occasionally with dolomite. Their very low carbon isotopic compositions (–61.0 < δ13C ‰ V-PDB < –40.1) suggest anaerobic oxidation of methane (AOM) as the main process controlling carbonate precipitation. The oxygen isotopic signatures (+2.4 < δ18O ‰ V-PDB < +6.2) lie within the range in equilibrium under present-day/interglacial to glacial conditions of bottom seawater; alternatively, the most positive δ18O values might reflect the contribution of 18O-rich water from gas hydrate decomposition. The frequent occurrence of diagenetic gypsum crystals suggests that reduced sulphur (hydrogen sulphide, pyrite) from sub-seafloor sediments has been oxidized by oxygenated bottom water. The acidity released during this process can potentially induce the dissolution of carbonate, thereby providing enough Ca2+ ions for pore solutions to reach gypsum saturation; this is thought to be promoted by the bio-irrigation and burrowing activity of benthic fauna. The δ18O–δ13C patterns identified in the authigenic carbonates are interpreted to reflect variations in the rate of AOM during the last glacial–interglacial cycle, in turn controlled by variably strong methane fluxes through the pockmarks. These results complement the conclusions of Kasten et al. in this special issue, based on authigenic barite trends at the Hydrate Hole and Worm Hole pockmarks which were interpreted to reflect spatiotemporal variations in AOM related to subsurface gas hydrate formation–decomposition.

Discharged drilling waste from oil and gas platforms and its effects on benthic communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 456:285-302 (2012) - DOI: https://doi.org/10.3354/meps09622 REVIEW Discharged drilling waste from oil and gas platforms and its effects on benthic communities J. I. Ellis1,*, G. Fraser2, J. Russell3 1Coastal & Freshwater Research Group, Cawthron Institute, Private Bag 2, Nelson 7010, New Zealand 2Faculty of Environmental Studies, York University, Toronto, Ontario M6H 1T5, Canada 3Alder Institute, Tors Cove, Newfoundland A0A 4A0, Canada *Email: joanne.ellis@cawthron.org.nz ABSTRACT: This review paper identifies the main effects of oil and gas drilling waste on benthic environments. We identified 26 papers and technical reports that surveyed sediment samples from 72 production or exploration platform sites to assess the zone of influence of sediment contamination and biological effects on benthic communities. While oil-based fluids are now rarely used in the marine context, their release has had large-scale (out to 6 km) and persistent (decadal time scale) impacts on benthic communities. The zone of influence of water-based drilling fluids as determined by sediment barium concentration was larger (2 to 20 km) than for synthetic-based fluids (200 to 2000 m). The zone of biological effects on benthic community diversity and abundance ranged from 100 to 1000 m for both water and synthetic fluids. Effects include changes in benthic species diversity, abundance and alterations to community structure. Functional changes included a loss of suspension-feeding species and increases in deposit feeders and polychaetes. In general, this review demonstrates a loss of benthic biodiversity and suspension-feeding communities due to oil exploration and production and the potential for large-scale effects on sensitive communities such as deep-sea, coral and vegetated habitats. Current research gaps and priorities are identified. KEY WORDS: Benthic community composition · Chemical toxicity · Organic enrichment · Suspended sediments · Oil-based fluids · Synthetic-based fluids · Water-based fluids Full text in pdf format PreviousCite this article as: Ellis JI, Fraser G, Russell J (2012) Discharged drilling waste from oil and gas platforms and its effects on benthic communities. Mar Ecol Prog Ser 456:285-302. https://doi.org/10.3354/meps09622 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 456. Online publication date: June 07, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

The New Bedford Harbor Superfund site long-term monitoring program (1993–2009)

New Bedford Harbor (NBH), located in southeastern Massachusetts, was designated as a marine Superfund site in 1983 due to sediment contamination by polychlorinated biphenyls (PCBs). Based on risks to human health and the environment, the first two phases of the site cleanup involved dredging PCB-contaminated sediments from the harbor. Therefore, a long-term monitoring program (LTM) was developed to measure spatial and temporal chemical and biological changes in sediment, water, and biota to assess the effects and effectiveness of the remedial activities. A systematic, probabilistic sampling design was used to select sediment sampling stations. This unbiased design allowed the three segments of the harbor to be compared spatially and temporally to quantify changes resulting from dredging the contaminated sediments. Sediment was collected at each station, and chemical (e.g., PCBs and metals), physical (e.g., grain size), and biological (e.g., benthic community) measurements were conducted on all samples. This paper describes the overall NBH-LTM approach and the results from the five rounds of sample collections. There is a decreasing spatial gradient in sediment PCB concentrations from the northern boundary (upper harbor) to the southern boundary (outer harbor) of the site. Along this same transect, there is an increase in biological condition (e.g., benthic community diversity). Temporally, the contaminant and biological gradients have been maintained since the 1993 baseline collection; however, since the onset of full-scale remediation, PCB concentrations have decreased throughout the site, and one of the benthic community indices has shown significant improvement in the lower and outer harbor areas.

Simplification of macrozoobenthic assemblages related to anthropogenic eutrophication and cyanobacterial blooms in two large shallow subtropical lakes in China

Eutrophication has become a serious problem in lakes in the middle and lower reaches of the Yangtze River, and is exerting profound pressures on the aquatic communities. However, little research has been conducted on the effects of eutrophication on benthic communities in these lakes. In this study, we investigated macrozoobenthic assemblages in two large shallow lakes (Lake Chaohu and Meiliang Bay in Lake Taihu), which have each experienced severe environmental deterioration and increased occurrences of cyanobacterial blooms in the past few decades. To analyze the changes in benthic community structure over the long-term, we compared the present community with communities from previous studies. Our results showed that present benthic assemblages have simplified substantially compared to communities in the past. In Meiliang Bay, Tubificidae and Chironomidae exclusively dominated the benthic community in 2007, in contrast with the relatively high diversity of benthic community in 1994, with several taxa sharing dominance of the community. Similarly, benthic assemblages in Lake Chaohu changed greatly over two decades, shifting from dominance by Bivalvia in 1980–1981 to dominance by Tubificidae and Chironomidae in 2008–2009. These observed changes in benthic assemblages are discussed relative to the ability of individual different taxa to tolerate eutrophication, algal blooms, Microcystins and associated habitat deterioration.

The recent history of the Tarquinia Salterns offers the opportunity to investigate parallel changes at the habitat and biodiversity levels

1 - Salterns, although artificial habitats, can be considered as coastal wetlands from an ecological, functional and conservational point of view, according to the Ramsar Convention Bureau (1990). Salterns need to be actively managed to survive and, being at the interface between land and sea, experience the impacts of both environments. For these reasons their extension and quality are severely reducing along the Mediterranean coasts. 2 - The Tarquinia Salterns, on the Tyrrhenian coasts of central Italy, suffered a progressive habitat degradation starting with a serious flood in 1987 and getting worse from 1997, when the salt production ceased, to 2003, when a three years long project for their environmental rehabilitation was implemented (2003 – 2006). 3 - To recover the salterns habitat, the water flow, previously slow and laminar, was re-established. Also, the depth of the water column was reinstated through the removal of the excess of organic matter and mud deposited in the pans. 4 - The recent history of the Tarquinia Salterns provides the opportunity to carry on multi-disciplinary studies on the response of biotic and abiotic habitat components under the temporal oscillations of the environmental quality. A first result is that the recovery succeeded in restoring the abiotic conditions characterizing the salterns before their abandon and degradation. 5 - The biodiversity at the genetic level, investigated on the killifish Aphanius fasciatus, at the species level, as shown by the abundance of wintering birds; and at the community level, as assessed by the diversity of benthic community, was seriously affected by the environmental degradation. After the ecological recovery, the species and community reverted quickly to the previous diversity levels, while the genetic variation of the target killifish remained at the low levels reached in 2005. This confirms that the different aspects of biodiversity react similarly to the disturbance but display different times of recovery.

Is benthic food web structure related to diversity of marine macrobenthic communities?

Numerical structure and the organisation of food webs within macrozoobenthic communities has been assessed in the European waters (Svalbard, Barents Sea, Baltic Sea, North Sea, Atlantic Ocean and the Mediterranean Sea) to address the interactions between biodiversity and ecosystem functioning. Abundance and classical species diversity indices (S, H′, J) of macrofaunal communities were related to principal attributes of food webs (relative trophic level and food chain length, FCL) that were determined from carbon and nitrogen stable isotope values. Structure of marine macrobenthos varies substantially at a geographical scale; total abundance ranges from 63 ind. m−2 to 34,517 ind. m−2, species richness varies from 3 to 166 and the Shannon-Weaver diversity index from 0.26 to 3.26 while Pielou’s evenness index is below 0.73. The major source of energy for macrobenthic communities is suspended particulate organic matter, consisting of phytoplankton and detrital particles, sediment particulate organic matter, and microphytobenthos in varying proportions. These food sources support the presence of suspension- and deposit-feeding communities, which dominate numerically on the sea floor. Benthic food webs include usually four to five trophic levels (FCL varies from 3.08 to 4.86). Most species are assigned to the second trophic level (primary consumers), fewer species are grouped in the third trophic level (secondary consumers), and benthic top predators are the least numerous. Most species cluster primarily at the lowest trophic level that is consistent with the typical organization of pyramidal food webs. Food chain length increases with biodiversity, highlighting a positive effect of more complex community structure on food web organisation. In more diverse benthic communities, energy is transferred through more trophic levels while species-poor communities sustain a shorter food chain.

Rapid Biodiversity Assessment and Monitoring Method for Highly Diverse Benthic Communities: A Case Study of Mediterranean Coralligenous Outcrops

Increasing anthropogenic pressures urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to explore present trends, detect future modifications and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex deep-water habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. Therefore, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We used an extensive photographic survey, covering several spatial scales (100s of m to 100s of km) within the NW Mediterranean and including 2 different coralligenous assemblages: Paramuricea clavata (PCA) and Corallium rubrum assemblage (CRA). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm2 for PCA and 2500 cm2 for CRA). In addition, we conclude that 3 replicates provide an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We contend that the proposed sampling approach provides a valuable tool for management and conservation planning, monitoring and research programs focused on coralligenous outcrops, potentially also applicable in other benthic ecosystems.

Foraminiferal biodiversity associated with cold-water coral carbonate mounds and open slope of SE Rockall Bank (Irish continental margin—NE Atlantic)

Cold-water coral (CWC) ecosystems are hotspots of macro- and microfaunal biodiversity and provide refuge for a wide variety of deep-sea species. We investigated how the abundance and biodiversity of ‘live’ (Rose Bengal stained) foraminifera varies with, and is related to, the occurrence of CWC on the Rockall Bank (NE Atlantic). Qualitative and quantitative analyses were performed on 21 replicate samples from 8 deep-sea stations, including 4 stations on CWC-covered carbonate mounds at depths of 567–657 m, and 4 stations on the adjacent slope at depths of 469–1958 m where CWC were absent. This sampling strategy enabled us to demonstrate that sediments surrounding the living CWC were characterised by higher foraminiferal abundance and biodiversity than open-slope sediments from the same area. A total of 163 foraminiferal species was identified. The dominant species in CWC sediments were: Spirillina vivipara, Allogromiid sp. 1, Globocassidulina subglobosa, Adercotryma wrighti, Eponides pusillus, Ehrenbergina carinata, Planulina ariminensis, Trochammina inflata and Paratrochammina challengeri. Foraminifera were nearly absent in adjacent open slope areas subject to strong tidal currents and characterised by coarse grained deposits. We suggest that CWC create a heterogeneous three-dimensional substrate offering microhabitats to a diverse benthic foraminiferal community.

Intertidal meiofauna communities along an estuarine gradient in a protected area (Ria de Foz, north-west Spain)

The northern Galician rias provide important economic and social services from fisheries, shellfish harvesting and recreational activities. Consequently, these rias have been included in the Nature 2000 Network as a Special Conservation Zone. The aims of this study were to describe the meiofauna spatial structure in terms of diversity and abundance of major taxa, as well as its relationship with the environmental characteristics in the Ria de Foz nature reserve. For this aim, environmental gradients and distribution patterns of intertidal meiobenthic communities at the Ria de Foz nature reserve were studied using multivariate methods. Ria de Foz showed to be a complex transitional habitat with significant changes in its environment along the estuarine gradient. An abundant and rich meiofauna community was reported at Ria de Foz. A total of 21 higher taxa of meiofauna were found. The most common taxa were nematodes, copepods, ostracods and turbellarians. Three clear different meiobenthic communities were defined. These three communities showed a clear spatial distribution pattern along the estuarine gradient. Moreover, a high degree of similarity between distribution patterns of meiobenthic communities and previously studied macrobenthic communities was found. Regarding the role of environmental factors shaping meiobenthic community distribution patterns distance to the river mouth was the environmental variable that best explained meiobenthic community structure and distribution. Therefore, changes on hydrodynamics that affect environmental factors related to the estuarine gradient will change the distribution pattern and diversity of benthic communities. This work provides the first information about meiobenthos diversity and structure in the Ria de Foz nature reserve and should be useful for future management and conservation plans on this and other similar protected areas.