Biomass Of Benthic Macrofauna Research Articles

How restoration engineering measures can enhance the ecological value of intertidal flats

Restoration engineering measures, such as managed realignments or building groins, modify the environmental characteristics of coastal intertidal ecosystems. Creating physical modifications that are beneficial to an intertidal system's ecology necessitates an in‐depth understanding of the relationships between the abiotic and biotic components of a given intertidal habitat. In this study, we evaluate how hydrodynamics and sediment characteristics drive the development of the benthic macrofauna community during the first 5 years following engineering measures to enhance benthic macrofauna diversity at three locations. The creation of low‐energy habitats through groins (Knuitershoek and Baalhoek) and a managed realignment dike breach (Perkpolder) led to the accumulation of fine sediments in all three impact sites. Biomass of benthic macrofauna quickly increased between 2016 and 2020, with successional processes being more important in Perkpolder, where the habitat was started completely from scratch due to a managed realignment, than at Knuitershoek or Baalhoek, where habitat conditions were improved by adding groins. In addition, the density of benthos‐eating birds, especially oystercatchers, increased at some of the modified sites. While a low‐energy habitat may harbor more diverse assemblages of benthic macrofauna than a highly dynamic one, the extremely high silt content, which is typical for low‐energy habitats, may slow benthic community development. The observed increase of biomass at our impact sites highlights the value of the interventions, while the delays in the response of the benthic macrofauna community emphasizes the need for extensive monitoring both in time and space and the identification of underlying abiotic–biotic mechanisms.

Low benthic mineralization and nutrient fluxes in the continental shelf sediment of the northern East China Sea

The sediment oxygen uptake rate, vertical distributions of organic carbon content, sedimentation rate, and benthic nutrient flux were measured from May 29 to June 9, 2015, to evaluate the partitioned organic carbon and nutrient cycles in the sediment of northern part of East China Sea. The sediment oxygen uptake rate, measured by in situ and/or ex situ incubation methods were ranged from 5.81 ± 0.08 to 16.36 ± 0.08 mmol O2 m−2 d−1. The fauna mediated oxygen uptake rate were ranged from 5.80 ± 0.04 to 8.09 ± 1.52 mmol O2 m−2 d−1, showing a strong relationship with the benthic macrofauna biomass and density. The burial flux of organic carbon into sediment layer ranged from 0.26 to 2.04 mmol C m−2 d−1 (average: 0.92 ± 0.64 mmol C m−2 d−1), which comprised 0.5–4.2% (average: 1.9 ± 1.3%) of primary production. Burial efficiency ranged from 2.0 to 22.4% (average: 11.1 ± 7.0%). Low sediment oxygen uptake rate caused low effluxes of dissolved inorganic nitrogen (0.19 ± 0.03–0.73 ± 0.04 mmol N m−2 d−1), phosphate (−0.034 ± 0.004–0.016 ± 0.005 mmol P m−2 d−1), and silicate (0.30 ± 0.03–1.61 ± 0.06 mmol Si m−2 d−1), which accounted for less than 10% of the nutrients required for primary production in the water column.

Influences of size structure and post-bloom supply of phytoplankton on body size variations in a common Pacific Arctic bivalve (Macoma calcarea)

The substantial loss of Arctic sea ice will alter marine ecosystems in many ways. Recent studies have reported a distributional shift in benthic macrofaunal biomass in the Pacific Arctic, likely caused by changes in food availability for benthic organisms. Here, we assessed the influence of differences in post-bloom supply of phytoplankton to the sediment on the growth of a common Pacific Arctic bivalve (Macoma calcarea) based on field and satellite observations, and feeding experiments. Among the sampling stations examined, the spatial distribution of M. calcarea body size showed clear variations and was associated with phytoplankton size structure during the post-bloom period. In addition, our feeding experiment exposing M. calcarea to different feeding treatments suggest that the continuous settlement of fresh phytoplankton is more important for the bivalve's growth than the total amount of phytoplankton settlement. This could explain the significant linkage between M. calcarea body size and phytoplankton size structure during the post-bloom period, because the larger phytoplankton represent an influx of fresh phytoplankton to the sediment and hereby support better growth and/or longevity of bivalves. Our study provides novel insights into a variety of processes related to the growth of M. calcarea and its relationship with the phytoplankton community.

Ecosystem resilience following salinity change in a hypersaline estuary

Salinity variability can act as a disturbance to communities in estuarine systems. Climate models predict changes in precipitation patterns will increase future hydrological variability, particularly in the southwestern United States. This study used infaunal community characterization, stomach content, and stable isotope analyses to evaluate the functioning of an estuarine food web over a range of wet and dry conditions. Baffin Bay is a predominantly hypersaline system in the semi-arid region of South Texas, USA supporting large populations of Pogonias cromis, black drum, a commercially important benthic predator. Salinity was the best predictor of changes in benthic macrofauna biomass, abundance, and diversity in Baffin Bay. Isotopic analyses of muscle tissues indicate that black drum use resources, particularly deposit-feeding benthic macrofauna, from both Baffin Bay and an adjacent system under normal estuarine salinity (≤35) conditions, but are more constrained to Baffin Bay under hypersaline (>35) conditions. This spatial restriction may be due to the energetic cost of osmotic regulation in hypersaline conditions, which can limit movement of euryhaline fish. Understanding the impacts of salinity change on benthic prey availability and trophic interaction dynamics is critical to determining ecosystem-scale effects of salinity variability.

Benthic-pelagic coupling in coastal seas – Modelling macrofaunal biomass and carbon processing in response to organic matter supply

Abstract Benthic macrofauna is an important component linking pelagic and benthic ecosystems, especially in productive coastal areas. Through their metabolism and behaviour, benthic animals affect biogeochemical fluxes between the sediment and water column. Mechanistic models that quantify these benthic-pelagic links are imperative to understand the functioning of coastal ecosystems. In this study, we develop a dynamic model of benthic macrofauna to quantify the relationship between organic matter input and benthic macrofaunal biomass in the coastal zone. The model simulates the carbon dynamics of three functional groups of benthic macrofauna and their sediment food sources and is forced by a hydrodynamic-biogeochemical model simulating pelagic physical and biological dynamics. The model reproduces measured time-series of macrofaunal biomass from two coastal sites with contrasting sedimentation in the Baltic Sea in 1993–2005 with comparatively high accuracy, including a major increase at one of the sites dominated by the bivalve Limecola (Macoma) balthica. This shift in community composition suggests altered pathways of organic matter degradation: 39% of simulated sedimentation was mineralised by macrofauna in 2005 compared to 10% in 1995. From the early 2000s onward macrofaunal biomass seems to be food-limited, as ca 80% of organic carbon sedimentation was processed by the deposit-feeding macrofauna at both sites. This model is a first step to help quantify the role of macrofauna in marine coastal ecosystem functioning and biogeochemical cycles and build predictive capacity of the effects of anthropogenic stressors, such as eutrophication and climate change, on coastal ecosystems.

Walrus haul-out and in water activity levels relative to sea ice availability in the Chukchi Sea

An animal's energetic costs are dependent on the amount of time it allocates to various behavioral activities. For Arctic pinnipeds, the time allocated to active and resting behaviors could change with future reductions in sea ice cover and longer periods of open water. The Pacific walrus (Odobenus rosmarus divergens) is a large Arctic pinniped that rests on sea ice or land between foraging trips to feed on the seafloor. We used behavioral data collected from radiotagged walruses in the Chukchi Sea (2008–2014) in a Bayesian generalized linear mixed effects model to estimate the probability a walrus was in water foraging, in water not foraging, or hauled out, as a function of environmental covariates. The probability of a walrus being in water increased with wind speed and decreased with air temperature, and the probability a walrus was foraging, given it was in water, increased with available benthic macrofaunal biomass. The probability of each behavior was also related to the nature and availability of haul-out substrates. The amount of time walruses spent in water foraging and hauled out was greatest when only sea ice was available, which typically occurs when walruses occupy feeding areas during summer and early autumn. This situation may be most energy efficient for walruses because it allows the highest proportion of in water energy expenditure to be allocated to foraging. Conversely, the amount of time walruses spent in water foraging and hauled out was lowest when only land was available, which typically occurs in late autumn, in years when walruses were constrained to land haul-outs because sea ice was absent over the continental shelf.

Generalized assessments of composition, quantitative distribution and biomass of benthic macrofauna on the shelf and slope in the North-West Pacific

Generalized assessments of composition, quantitative distribution and biomass of benthic macrofauna on the shelf and slope in the North-West Pacific

Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic

Abstract. Long-term experimental studies suggest that, under transient anoxic conditions, redox fronts within the sediment shift upwards, causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) and S(-II)). Infaunal benthic organisms are associated with different redox fronts as micro-habitats and must be affected by such changes during natural hypoxia events. In order to document the geochemical evolution of the sediment during prolonged anoxia in the framework of an in situ experiment designed to mimic natural conditions, benthic chambers were deployed on the seafloor of the Northern Adriatic and sampled after 9, 30 and 315 days of incubation. Oxygen and sulfide were measured continuously in the early stages (9 days) of the experiment. High-resolution pore water profiles were sampled by DET probes and redox-sensitive species (S(VI), Mn(II) and Fe(II)) and alkalinity were measured. Starting oxygen saturation was about 80% within the chamber. After 7 days, anoxia was established in the bottom waters within the chambers. Mn(II) and Fe(II) started diffusing towards the anoxic water column until they reached the surficial sediment. Being reoxidized there, Mn and Fe reprecipitated, giving a rusty coloration to the seafloor. Infaunal species appeared at the sediment surface. After 20 days, all macro-organisms were dead. Decomposition of macro-organisms at the sediment–water interface generated S(-II) within the entire height of the chamber, leading to a downward flux of sulfides into the sediment, where they were quickly oxidized by metallic oxides or precipitated as FeS. S(-II) was below detection in the water column and pore waters at the end of the experiment. Our results suggest that S(-II) enrichment in the water column of coastal systems, which are episodically anoxic, is strongly controlled by the biomass of benthic macrofauna and its decay during anoxia, whereas its residence time in the water column is controlled by iron availability (as solid oxides or as dissolved reduced cations) within the sediment, even without water circulation.

Linking terrestrial and benthic estuarine ecosystems: organic matter sources supporting the high secondary production of a non-indigenous bivalve

The Asian clam, Corbicula fluminea, is among the most pervasive invasive species in freshwater ecosystems worldwide. Our objective was to study C. fluminea’s functional response in terms of feeding behavior and food selectivity, using the natural variation in organic matter (OM) sources that occur in estuarine environments. Using C and N stable isotopes, we identified and quantified the contribution of different OM sources supporting the production of C. fluminea along the salinity gradient occupied in the Minho River estuary (NW-Iberian Peninsula, Europe), where this species presently dominates the benthic macrofauna biomass. We observed a pronounced shift in the quality of OM available for C. fluminea along the estuarine mixing zone. Stable isotope analysis, POM C/N, and phytoplankton contribution estimates based on C:Chl a revealed that POM was largely comprised of terrestrial-derived OM in tidal freshwater stations (TFW) and was increasingly comprised of phytoplankton, a more palatable food source, towards the polyhaline estuary. A similar shift in the isotopic composition along the estuarine mixing zone was observed in C. fluminea, suggesting a shift in food resources. Accordingly, based on a Bayesian stable isotope mixing model, there was an upstream–downstream counter gradient in the contribution to C. fluminea biomass from terrestrial-derived OM (41–64 % in TFW) and phytoplankton (29–55 % in the brackish estuary). Although the majority of the food sources identified were filtered from the water column (70–80 %), reliance on sediment OM and microphytobenthos provided evidence for deposit feeding by C. fluminea. We conclude that C. fluminea has the ability to adapt to environments with low food quality because it can consume terrestrial-derived OM. This can be a competitive adaptation in systems with perennial low food quality such as the Minho River estuary. Moreover, its ability to couple benthic and pelagic environments and terrestrial ecosystems demonstrates a strong potential to alter food web flows in aquatic ecosystems.

Macroinfauna Dynamics and Sediment Parameters of a Subtropical Estuarine Lake—Coombabah Lake (Southern Moreton Bay, Australia)

Dunn, R.J.K.; Lemckert, C.J.; Teasdale, P.R., and Welsh, D.T., 2013. Macroinfauna dynamics and sediment parameters of a subtropical estuarine lake—Coombabah Lake (Southern Moreton Bay, Australia).The distribution, composition, density, and biomass of benthic macrofauna within estuarine environments typically exhibit significant variations attributable to heterogeneity in and interactions between physical, biological, and chemical processes. The spatial and temporal dynamics of benthic macroinfauna assemblages and physicochemical sediment parameters within the intertidal mudflats of a subtropical estuarine lake (Coombabah Lake, Southern Moreton Bay) were studied at four sites from August 2006 to April 2007. No significant seasonal changes were observed at any site for all physical sediment parameters. The northern sample sites were characterised by fine- to medium-grained to moderately to poorly sorted sediments and the southern sample sites by fine-grained to moderately well to well-sorted. A total of 1029 individuals representing species from three orders, including deposit feeding and filter feeding macroinfaunal groups, were collected. The highest combined species densities occurred in the fine-grained southern sites, with the greatest combined species density occurring at Site 4 during winter. Amphipods (Victoriopisa australiensis) and polychaete worms (Simplisetia aequisetis) dominated the lake-wide faunal community with V. australiensis, representing 49% of the total retrieved macroinfauna. Significant correlations between mean macroinfauna densities, biomassDW, sediment parameters, and seasonal maximum monthly temperatures were identified during the study. Seasonal trends in combined site densities were observed at each of the lake sites, with the highest combined density occurring during winter. Spatial and temporal variations might also be partially explained by the predation pressures of fish and migratory wading birds within the lake, with the seasonal presence of migratory wading birds coinciding with the minimum observed macroinfauna densities at each sample site.

Influence of a microhabitat on the structuring of the benthic macrofaunal community in a mangrove forest

Habitat heterogeneity contributes to the maintenance of species diversity; however, little is known about the influence of microhabitat heterogeneity on the diversity of mangrove invertebrates. We tested the hypothesis that the structures of benthic faunal communities differ among microhabitats because each microhabitat function differs widely according to their physical properties. The descriptors of invertebrate assemblages were determined every March (dry season) and August (wet season) of 2005, 2006, and 2007 in three different mangrove microhabitats—tidal creek, deep forest, and canopy gap—of an intertidal mangrove forest around the Sikao Creek in the Trang Province of southern Thailand. The physical properties of the selected microhabitats were studied in 2005. The properties of each microhabitat varied, especially with respect to the light intensity and sediment moisture content: the tidal creeks were wet and well-exposed to sunlight, forest interiors were moist and dark, and the canopy gaps were dry and well-exposed to sunlight. Seasonal differences in the microhabitats were also noted. The numerical abundance and biomass of benthic macrofauna differed among the microhabitats; both values were the highest in canopy gaps, and these values increased in the wet season. Despite seasonal differences, species composition differed in the three microhabitats; the majority of animals were members of the epifauna; these were surface deposit feeders. Each microhabitat functioned differently because their physical properties were disparate. A diverse benthic faunal community is formed by a combination of different functional microhabitats in mangrove ecosystems, thereby indicating that microhabitat heterogeneity should be considered as an important factor influencing the structuring of a benthic community.

Initial recolonization of benthic fauna in defaunated sediment contaminated with octylphenol: Field microcosm exposure study

Recolonization of benthic fauna in defaunated sediment contaminated with octylphenol (OP) has been investigated by the use ofin situ microcosm exposure study. Trays with defaunated sediment (control) and those treated with five OP concentrations (0.59, 5.4, 7.6, 66, and 660 μg g−1, sediment dry weight (DW)) were exposed at the subtidal (ca. 10 m), in the southern coast of Korea, over two months. The initial response (after one-month exposure) of macrozoobenthos at the trays of control and three lower OP (0.59–7.6 μg g−1 DW) showed rapid colonization of macrozoobenthos with high diversity and abundance. However, the species number sharply decreased after two-month exposure, particularly at the tray of greatest OP (660 μg g−1 DW) treated with species number from 15 (after 30-days) to 3 (after 70-days). Other univariate indices such as abundance and biomass of benthic macrofauna also showed concentration-and time-dependent declines, indicating a potential adverse effect of OP on benthic community recolonization. Further, the multi-dimensional scaling (MDS) analysis that clearly separated two distinct faunal groups of macrobenthos during exposure supported the concentration-dependant recolonization followed by succession at the OP concentration of >7.6 μg g−1 DW. Similar to macrofauna, the meiofaunal abundance significantly decreased at the OP concentration of >7.6 μg g−1 DW, indicating certain threshold of OP between 7.6–66 μg g−1 DW that caused adverse effect on benthic community recolonization. Although the critical adverse OP concentration found in community level was relatively high compared to the environmental concentrations (ppb levels) reported in coastal sediments, it should be pointed out that certain species could be influenced by the exposure of lower OP concentrations.

Sea-level rise, expected environmental changes, and responses of intertidal benthic macrofauna in the Humber estuary, UK

In many European estuaries, extensive intertidal habitats could vanish in the future due to rising sea levels that squeeze tidal flats against established sea defences. The remaining intertidal area is likely to become steeper with coarser sediment, and saline water may intrude upstream due to increased water depth and enhanced wave energy. This paper investigates the impacts of sea-level rise on benthic macrofauna in an intertidal habitat in the Humber estuary, UK. Field surveys were conducted between 2003 and 2004 to examine spatial patterns of benthic macrofaunal biomass along the estuarine longitudinal gradient and the local beach width gradient. Multiple regression analysis revealed that >80% of the observed variation in biomass of the 2 dominant bivalve species Macoma balthica and Cerastoderma edule, and the total biomass of other macrobenthic species, could be explained by key environmental variables such as salinity, sediment characteristics and morphological factors. Physical data for the Humber estuary were assessed to predict the likely course of changes in these key environmental variables in response to sea-level rise. Model simulations showed that a sea-level rise of 0.3 m would result in a 6.7% loss of intertidal area and 6.9% loss of total macrobenthic biomass, and that saline intrusion could partly compensate for such loss of macrobenthic biomass. However, associated environmental changes, such as beach slope steepening and sedimentary shifts, could have overriding negative impacts with potential loss of macrobenthic biomass of up to 22.8%, depending on the extent of environmental changes.

Spatial distribution of macrofauna in a littoral zone with drifting macroalgae in the Neva estuary

This study focuses on the influence of drifting algae (Cladophora glomerata) and oxygen depletion on the distribution and biomass of macrofauna in the shallow stony-sandy littoral of the Neva estuary, easternmost part of the Baltic Sea. Great masses of decaying drifting algae (315- 445 g dry weight m -2 ), oxygen depletion (5.4-24.5% or 0.6-2.8 mg L -1 ), and subsequent low bio- mass of macrofauna (0.5-2.9 g wet weight m -2 ) were recorded in the near-shore area (5-20 m). At greater distances (30−60 m from the shore) the biomass of drifting algae decreased, hypoxia was not recorded, and no internal significant differences in the total biomass of benthic macrofauna (24.3-30.8 g wet weight m -2 ) were found. The biomass of the macroinvertebrate community of the drifting algae reached 4.1-5.5 g wet weight m -2 at distances of 10-20 m from the shore, and was at least 20 times lower in the area closest to the shore (5 m). Amphipods and chironomids contributed to the total biomass 42% and 26%, respectively. Species with opportunistic life strategies and high resistance to oxygen depletion are able to survive and dominate in coastal areas of the Neva estuary with temporary hypoxia induced by macroalgal decomposition.

Summer influence of 1 and 2 yr old mussel cultures on benthic fluxes in Grande-Entrée lagoon, Îles-de-la-Madeleine (Québec, Canada)

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 338:131-143 (2007) - doi:10.3354/meps338131 Summer influence of 1 and 2 yr old mussel cultures on benthic fluxes in Grande-Entrée lagoon, Îles-de-la-Madeleine (Québec, Canada) Marion Richard1,2,3, Philippe Archambault1,3,*, Gérard Thouzeau2, Gaston Desrosiers3,† 1Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Environmental Sciences Division, 850 Route de la Mer, PO Box 1000, Mont-Joli, Québec G5H 3Z4, Canada 2CNRS-UMR 6539, Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, Place Nicolas Copernic, 29280 Plouzané, France 3Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 Allée des Ursulines, CP 3300, Rimouski, Québec G5L 3A1, Canada *Corresponding author. Email: philippe_archambault@uqar.qc.ca†In memoriam ABSTRACT: The summer influence of 1 and 2 yr old suspended mussel lines on benthic fluxes (oxygen, silicates, ammonium, phosphates, nitrates and nitrites) was studied in Grande-Entrée lagoon (GEL), Îles-de-la-Madeleine, Québec, Canada. This influence and its temporal variation were examined in relation to bottom water, sediment and macrofauna characteristics. In situ mensurative experiments using benthic chambers and sediment cores were carried out at 2 mussel sites (M1 and M2) and 2 control sites (C1 and C2) in July, August and September 2003. In contrast to 1 yr old mussel lines (M1), 2 yr old lines (M2) enriched the sediment in organic matter and increased silicate, ammonium, phosphate and nitrite fluxes at the water–sediment interface. Silicate, ammonium and phosphate fluxes were highest in August, when temperature was highest. The main nutrient releases observed at the water–sediment interface in M2 could reduce nitrogen and silica limitation in the water column. Mussel lines did not influence benthic macrofauna biomass, but favoured the recruitment of many small-sized organisms. No influence of mussel lines was observed on oxygen consumption at the water–sediment interface. Macrofauna biomass and oxygen consumption increased in parallel during the summer, but the respiration of the low biomass alone cannot explain the greater overall benthic oxygen demand. The latter was probably also driven by the oxidation of reduced compounds such as sulfides. The reduced nature of the sediment could be natural in GEL, but the continuous accumulation of mussel biodeposits since 1985 has probably contributed to the degradation of the benthic environment in the mussel farm. KEY WORDS: Mussel line · Biogeochemical fluxes · Water–sediment interface · Organic enrichment · Benthic macrofauna Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 338. Online publication date: May 24, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

A descriptive account of benthic macrofauna and sediment from an area of planned petroleum exploration in the southern Caspian Sea

As a precursor to petroleum exploration and potential development in the offshore southern Caspian Sea, sediment was collected from 42 stations (67–692 m water depths) and analyzed for grain size, total organic carbon, and species abundance, diversity, and biomass of benthic macrofauna. Sediment ranged from very fine sands to very fine silts, with moderately enriched organic carbon levels (avg. 2.3%). A significant positive correlation between finer grain size, organic carbon, and water depth was evident. The macrofauna was numerically dominated by annelid worms (44% of total organisms), crustaceans (37%), and molluscs (18%). Of 71 species identified, the greatest diversity was represented by two crustacean orders (22 amphipod species, 11 cumacean species), 14 gastropod mollusc species, and six oligochaete worm species. Except for annelids, all major taxa exhibited significant decline in abundance, species density, and biomass with increasing water depth. Low species dominance and abundance characterized deeper stations, indicating stressed habitat from hypoxia/anoxia at the sediment–water boundary. Petroleum exploration and development at slope depths greater than 150 m should have relatively little impact upon a macrofauna that is naturally impoverished due to oxygen deficiency. Shelf depths (<150 m) are not oxygen limited and support a more diverse macrofaunal community, which could be more vulnerable to discharged cuttings and adhered drilling muds, but able to recover more quickly than deeper biota.

Impacts of water depth, sediment pigment concentration, and benthic macrofaunal biomass on sediment oxygen demand in the western Arctic Ocean

We investigated the impacts of water depth, sediment pigment concentration, and benthic macrofaunal biomass on sediment oxygen demand (SOD) during three cruises to the western Arctic Ocean. SOD values were similar to those of most studies from the Arctic and ranged from a high of 20.68 mmol O2·m–2·day–1 at a shallow shelf station to a low of 0.29 mmol O2·m–2·day–1 at the deepest basin station (3648 m). SOD was significantly greater at shallow sites (&lt;500 m; mean = 7.39 mmol O2·m–2·day–1; standard deviation (SD) = ±5.38) than at deep sites (&gt;500 m; mean = 1.39 mmol O2·m–2·day–1; SD = ±0.96). As hypothesized, SOD was negatively correlated with water depth and positively correlated with both surface-sediment pigment concentration and macrofaunal biomass, with macrofaunal biomass explaining approximately 74% of the variability in SOD. We propose that higher macrofauna-normalized respiration rates (i.e., SOD divided by macrofaunal biomass) in deep water indicate that microbial–meiofaunal respiration predominates in deep versus shallow water. Finally, deeper stations associated with Barrow Canyon had SODs, benthic macrofaunal biomass, and surface-sediment pigment concentrations that were similar to those of shallower shelf locations, suggesting down-canyon transport of organic material.

Using short-term growth of enclosed 0-group European flounder, Platichthys flesus, to assess habitat quality in a Danish bay

Summary Instantaneous growth rates of 0-group European flounder, Platichthys flesus, obtained from two 9-day enclosure experiments were used to assess the relative quality of three eelgrass and three bare sand habitats in the Bay of Aarhus, Denmark. Measurements of temperature, dissolved oxygen, salinity, sediment structure and biomass of benthic macrofauna were made during the experiments. Gut content analysis was performed after retrieval of the fish. Growth rates of flounder at two bare sand sites were higher or equal to growth rates at the three eelgrass sites, and at a muddy bare sand site in both experiments. The variation in gut fullness of flounder between vegetated and bare sand sites followed the pattern observed in growth rates, but diverged from the spatial variation in prey abundance, which indicates that there were differences in the feeding efficiency between sites. Overall, habitat complexity, i.e. the presence or absence of vegetation seems to be the most important factor determining the growth rates and, by corollary, habitat quality for juvenile European flounder in the Bay of Aarhus.

The effect of the 1997-1998 ENSO on the benthic macrofaunal biomass in the southwestern Gulf of Mexico

Se llevaron a cabo mediciones de biomasa macrofaunal, desde 1987, con el objeto de evaluar el efecto episódico de incorporación de carbono biogénico durante el evento de ENOS en el bentos de la plataforma continental y talud del suroeste del Golfo de México. Este estudio se basó en la hipótesis que la mezcla generada en la superficie del mar por el viento en periodos prolongados promueve una productividad primaria mayor en el Golfo de México que es exportada a profundidad y sostiene tróficamente la comunidad béntica, incrementando la biomasa de macrofauna. El contenido de nitrógeno orgánico en sedimento se empleó para expresar el enriquecimiento orgánico del sedimento. Los cambios geográficos y estacionales se han registrado con anterioridad en la región reconociendo que el máximo de biomasa macrofaunal ocurre durante la presencia de una condición de mezcla de la columna de agua y disminuye con el inicio del período de estratificación. La biomasa macrofaunal registrada en 1998 fue mayor que los valores de biomasa registrados en años anteriores (plataforma 0.93±0.22 gC.m-2, talud 0.55±0.23 gC.m-2), pero siguiendo una tendencia similar estacional (plataforma 0.57±0.11gC.m-2, talud 0.18±0.09 gC.m-2). La biomasa macrofaunal sobre la plataforma mostró una variabilidad amplia durante el período de estudio en contraste con los valores registrados sobre el talud. Como característica común del seguimiento de los registros a largo plazo se reconoció que las medidas de aportes estacionales de fitodetritos conllevan a un enriquecimiento del sedimento y se correlacionan con cambios de biomasa macrofaunal (plataforma r= 0.77; talud r= 0.85). El evento de teleconección ENOS promueve, a partir del forzamiento por viento, pulsos estocásticos de detrito de origen fotoautotrófico que enriquecen el sedimento y permiten un incremento significativo de la biomasa macrofaunal.doi: sin doi

Nutrient Retention by Benthic Macrofaunal Biomass of Danish Estuaries: Importance of Nutrient Load and Residence Time

The response of macrobenthic faunal abundance and biomass to nutrient load, and factors that may modify this response are examined by means of inter-estuary comparisons of 14 shallow Danish estuaries. Data for this analysis are the physicochemical and biological variables monitored by local authorities mainly during the period 1989–95. A clear positive effect of nutrient load is demonstrated on benthic biomass, over a wide range of total N-load as the model substance from 2–200gm−2year−1. The relationship was curvilinear with a levelling off or even depression of biomass at high total N-load (above c. 35gm−2year−1). A mixed chemostat model using total load and hydraulic residence time for estuaries was applied to estimate the load that could be realized into primary production, and consequently enter into benthic production. Two measures, the load corrected for winter export (the realized N-load) and the nutrient pool available for the spring bloom (SBNP) were calculated. The benthic metabolic demand inferred from biomass, assuming an annual P:B ratio of 1 (P, secondary production; B, benthic biomass), was approximately of the same magnitude as both total N-load and realized N-load. A positive correlation was still found between benthic biomass/production and the realized N-load, but the linearity of the regression between them was not improved compared to the corresponding relationship with total load. The best linearly proportional relationship was obtained with the spring bloom N-pool (SBNP) calculated from the chemostat model. Stoichiometry suggested, however, that the spring bloom is of little importance for supporting benthic standing stock in these well flushed estuaries. To explain the strong statistical relationship, despite poor causality, with SBNP, it is suggested that the algorithm behind SBNP reflects the ability of the estuary to retain nutrients in the water mass in the productive period, both as free molecules and included into biological particles. These findings strongly indicate that benthic standing stock system-wide is food limited and indicate the importance of interaction between loading and estuary residence time (flushing) for the outcome of eutrophication. The findings are in agreement with reports that high estuary flushing rate may modify effects of eutrophication, and they deviate from previous studies in shallow coastal areas reporting either no effect, or negative effects, of eutrophication on benthic biomass.