Composition Of Benthic Macrofauna Research Articles

Benthic macroinfaunal communities of the pockmark fields in the south-eastern Bay of Biscay

Pockmarks are concave depressions on the sea bottom produced by fluid escape from subaqueous sediments which can be found worldwide in muddy and silt/clay sediments. Due to their morphological and geochemical characteristics, certain pockmarks play an important role in structuring benthic communities, and consequently, they have been proposed to be protected. The present research provides a characterisation of the benthic macrofauna composition in pockmark fields in the southeaster Bay of Biscay. A total of 11 samples were acquired in and close to pockmarks covering a range of depths of 414–992 m. The survey strategy considered the acquisition of one sample inside of each of the selected pockmarks and another sample near, but out of them. Collected macrofaunal organisms were identified at lowest taxonomical level (species) when possible, structural parameters were calculated and a hierarchical cluster analysis carried out with species data. Species density, biomass, richness, diversity and evenness were found to be higher in samples collected inside pockmarks in comparison to samples obtained outside but not statistically significant. This could be explained by the inactivity of the studied pockmarks, which do not offer/generate a particular environment with unusual characteristics that limit or enhance the development of specific species/groups with special traits.

Variation in fatty acid content among benthic invertebrates in a seasonally driven system

AbstractAt temperate latitudes where seasonal changing environmental conditions strongly affect the magnitude, duration and species composition of pelagic primary production, macrobenthic organisms living below the photic zone rely on the sedimentation of organic matter as their primary energy source. The succession from nutritious spring blooms to summer cyanobacteria is assumed to reduce food quality for benthic primary consumers and their fatty acid (FA) profiles. In contrast, we find low seasonal variability in FA content of five benthic macroinvertebrates spanning two trophic levels in the Baltic Sea, a system with high seasonal variation in phytoplankton species composition. However, levels of the major FA groups vary greatly between benthic species. The results suggest that benthic macroinvertebrates have evolved FA metabolism adapted to degraded sedimenting material. Moreover, our study shows that species composition of benthic macrofauna rather than seasonal changing conditions affect availability of essential nutrients to higher trophic levels.

New insights into the benthic macrofauna composition and structure in a southern-west Mediterranean coastal lagoon after restoration actions: Spatial and Seasonal patterns

The Marchica lagoon (Morocco, Alboran Sea), one of the largest lagoons in the Mediterranean, was subject to various restoration actions in 2011 aiming at enhancing its biodiversity and ecosystem services. Here, benthic macrofauna was investigated (28 stations sampled seasonally in 2015) to assess the functioning on the lagoon after these restorations actions. The ultimate aim was to investigate the spatial and seasonal variation of the benthic macrofauna, the environmental drivers, and the potential effects of the recent bioinvasions. Overall, 131 taxa were identified among which two non-indigenous species (NIS) were recorded: Caprella scaura and Paracerceis sculpta. Multivariate analysis of abundances (cluster analysis and non-metric multi-dimensional scaling) allowed the identification of three main groups of stations totalizing seven macrofaunal assemblages. The species which are dominant and/or discriminate each assemblage are Cymodoce truncata, Elasmopus rapax, Ericthonius brasiliensis, Gammarus insensibilis, Heteromastus sp., Aonides oxycephala, Nereis sp., Loripes orbiculatus, P. sculpta and C. scaura. The macrofaunal assemblage composition are subject to seasonal changes, supported by significant differences in several univariate measures, including total number of individuals, number of taxa, and Shannon–Wiener’s diversity index. Furthermore, the Marchica lagoon showed high values of macrofaunal species richness further supporting the idea that the restoration measures had positive consequences. The distribution of the macrobenthic fauna in the study area was affected by a complex of various factors, with depth, temperature, salinity, sediment characteristics and vegetation biomass being the most important predictor variables. Macrofaunal assemblages significantly correlated with environmental variables; and exhibited a “High” to “Good” status in terms of the impact of alien species according to the Alien Biotic Index. However, the high abundance of NIS detected suggests caution about their impact and further spread.

Macrofauna abundance and diversity patterns of deep sea southwestern Gulf of Mexico

The diversity and distribution of macrofaunal communities in the deep-sea bottoms of Gulf of Mexico (GoM) Mexican waters are poorly known compared to the northern GoM. This study was designed to contribute to the knowledge of macrofauna communities through (i) evaluate the taxonomic composition of macrofauna communities at major taxa level, and (ii) analyze the spatial distribution patterns in the deep sea of the southwestern GoM. Benthic macrofauna composition was analyzed in a large geographical area (92.67°–96.70° W 18.74°–23.04° N) and bathymetric gradient (185-3740 m depth). Samples were collected on board the R/V Justo Sierra (Universidad Nacional Autónoma de México) with a Reineck-type box corer during the oceanographic cruises SOGOM-3 and SOGOM-4 carried out on April 21–May 15, 2017, and on August 29–September 20, 2018, respectively. Thirteen environmental parameters were measured (among them, depth, salinity, temperature, O2, sediment grain size, hydrocarbons, and organic matter). Twenty-five taxa were registered in SOGOM 3 (2315 individuals) all of which were observed in SOGOM 4 (1721 individuals) with exception of the mollusk Class Solenogastres. The average abundance (ind. m-2) registered was 517 (range: 150-1388 ind. m-2), and 347 (range: 38-1088 ind. m-2) for SOGOM 3, and SOGOM 4, respectively. In SOGOM 3 Polychaeta, Nematoda, Amphipoda, Tanaidacea, and Bivalvia contributed with 75% of the total abundance, which were also the most abundant in SOGOM 4 representing 82% of total macrofauna abundance. Highest abundance was registered to the south of the study area near the coast, and the lowest one was found in deeper areas. Macrofauna abundance decreased with depth in both cruises. High diversity values were registered at intermediate depths in the south and west zones of the study area. Both cruises separated in a nMDS analysis. During SOGOM 3 dissolved oxygen, aromatic hydrocarbons, and organic matter (%) were the environmental variables related to macrofauna whereas, in SOGOM 4, depth was the most important one. This study fills a gap in the knowledge of diversity and distribution of macrofaunal communities of the deep-sea bottoms of a large area covering the whole bathymetric range of southern Gulf of Mexico and provides a baseline useful to compare with polluted areas and for assessing the impact of chronic pollution and/or potential oil spill accidents.

Soft-bottom macrozoobenthos in semi-enclosed coastal systems of Morocco: A latitudinal and biogeographic analysis

Although soft-bottoms are the largest ecosystem on Earth in terms of area, only a small percentage of their macrobenthos has been studied and most of its species are not yet described. Herein, the most up-to-dated comprehensive inventory and the broad-scale baseline of the soft-sediment macrozoobenthos in semi-enclosed coastal systems (SECS) of the Moroccan Atlantic and Mediterranean coasts (3500 km) is presented. In total, 496 species (7 phyla, 21 classes, 65 orders and 201 families) were recorded among which 95 species were exclusively Mediterranean, 99 species were Atlantic–Mediterranean and 302 species exclusively Atlantic.The best multivariate model, explaining 33% of the total variation observed in benthic assemblages’ composition, included the type of the SECS (estuaries vs lagoons vs bay), the marine ecoregion (Atlantic vs Mediterranean), the surface of the SECS and the environmental features (minimal temperature, minimal and maximal salinity) as predictors of benthic macrofauna composition in the Moroccan SECS. In contrast to the general latitudinal diversity gradient (LDG) pattern, our results showed that species richness and taxonomic diversity showed no relationship with latitude. Such differences in benthic macrofaunal composition across a large scale could result from the fact that each ecosystem has its own specific characteristics, which implies an individualistic approach to ecosystem ecology.The sample of the 12 SECS considered in this study covers most of the range of variation along the coasts of Morocco. The current compilation is relevant in such poorly known area at the global scale and fulfills a knowledge gap on benthic macrofauna in SECS of the Southern part of the North-Eastern Atlantic and Mediterranean ecoregions. However, the knowledge gained here is insufficient to address perceived shortfalls in knowledge of biodiversity, its importance to ecosystem function, and the threats and consequences of disturbance by anthropogenic activities.

Spatial scale drives diversity patterns of benthic macroinvertebrate communities in tropical estuaries

AbstractIdentifying the hierarchical spatial levels that show the greatest dissimilarities between communities and how these patterns are generated is essential to provide insights into the monitoring and protection of biodiversity. In this study, we additively partitioned diversity of macroinvertebrates into alpha, beta, and gamma diversity across multiple scales in typical and semi‐arid tropical estuaries. We also determined which components of the total beta diversity, in terms of species replacement or richness difference (presence‐absence data) and abundance difference (relative abundance data), had the greatest relative importance in structuring the composition of benthic macrofauna. In typical and semi‐arid tropical estuaries, a non‐random spatial pattern was observed in additive partitioning of diversity, with higher values of beta diversity obtained at the largest scales analyzed. When considering the presence‐absence data, in general there was no clear trend which components of beta diversity had greater relative importance in typical estuaries. In the semi‐arid tropical estuaries, the richness difference component showed greater relative importance in the rainy season, whereas the species replacement presented greater proportions in the dry season. When considering abundance data, in general the abundance difference component showed greater relative importance in typical and semi‐arid tropical estuaries in the two seasonal periods. Therefore, approaches based on the presence/absence and on the relative abundance of species provided complementary answers about the distribution patterns of benthic macroinvertebrate communities. We demonstrated that environmental filtering and dispersal limitation may affect the patterns of distribution of benthic macrofauna in estuaries located in regions with different climatic conditions.

Effects of fish cage culture on macrobenthic communities in a subtropical river

Abstract. Tania NJ, Hossain MB, Habib, A, Musa N. 2020. Effects of fish cage culture on macrobenthic communities in a subtropical river. Biodiversitas 21: 3583-3589. The present study described the impact of freshwater fish cage culture on macrobenthic faunal assemblages in the Dakatia River, Chandpur, Bangladesh. The experimental design involved the establishment of four stations in two study sites, two stations near the culture area, and two stations away from culture area. A total of 23 macrobenthic taxa belonging to annelids, molluscs, arthropods, and other minor phyla were recorded from study sites. Oligochaetes were found to be dominant at all four stations composing 42.34% of the total macrobenthos. Pollution indicator benthic organisms i.e., Naididae (30.32%), Tubificidae (20.16%), and Chironomidae (3.54%) were found most in the cage culture area. The density of benthic macrofauna was higher (28,134 inds./m²) in the cage culture site than the non-cage culture site (4,358 inds./m²) due to high abundance of certain pollution tolerant species. However, the values of diversity indices i.e., Species Richness (SR), Shannon-Wiener (S-W) diversity (H´), Pielou’s evenness (E), and Margalef (J) were consistently higher in non-cage culture area than the cage culture area. One-way ANOVA showed no significant variation (P > 0.05) in diversity values between the sites. The results of the present study revealed effects of cage culture on the abundance, diversity, and composition of benthic macrofauna.

Climate-driven changes in macrobenthic communities in the Mediterranean Sea: A 10-year study in the Bay of Banyuls-sur-Mer.

Marine ecosystems worldwide are affected by both natural variation and human activities; to disentangle and understand their individual role in influencing the macrobenthic community composition is challenging. The relationship between interannual variability in atmospheric circulation, dictated by the climatic oscillation indices, and the benthic macrofauna composition was assessed at four sampling sites located in the Bay of Banyuls‐sur‐Mer (NW Mediterranean Sea). Between 2004 and 2013, these sites were sampled annually during autumn/winter and analyzed for sediment grain‐size and benthic macrofauna composition (species richness, abundance, and biomass). Temporal changes in these descriptors were correlated with two climatic indices (NAO and WeMO indices) and a set of environmental parameters integrated over three different time periods (i.e., whole year, springtime, and wintertime). Our results confirm the occurrence of major temporal changes in the composition of macrobenthic communities within the Gulf of Lions. More specifically, the results indicate that (a) the WeMO appears to be more closely related to benthic macrofauna composition in the Bay of Banyuls‐sur‐Mer than the NAO, (b) winter is a better integration period than spring or the whole year as a proxy for community composition changes, and (c) Rhône River water flow is likely involved in the control of benthic macrofauna composition in the whole Gulf of Lions. The present study highlights the importance of WeMO as a regional proxy, which can be used to evaluate changes in benthic macrofauna linked to climatic variability.

Benthic macrofaunal dispersion within different mangrove habitats in Hara Biosphere Reserve, Persian Gulf

The community composition of benthic macrofauna and relationships between physiochemical parameters of the water and sediment texture were assessed in Hara Biosphere Reserve, Northern Persian Gulf. The spatial distribution and diversity of macrobenthos were sampled within three distinctive mangrove zones (deltaic, island and coastal) during two sampling seasons between August 2014 and January 2015. A total of nine transects perpendicular to the coastline were selected to cover over the entire study area. The counts of all macrofauna were recorded from each zone and station with three replicate sediment samples. The snails, Cerithidea cingulata and Asseminea sp., were observed throughout three mangrove zones, but their abundance varied among habitats. The bivalve Dosinia ceylonica found to be more abundant in delta, whereas burrowing crabs Ocypode and Uca were dominate in coastal zone. Terebralia palustris and amphipods were recorded frequently in island zone. The nonmetric multidimensional scaling ordinations and a three-way factor PERMANOVA indicated that macro-invertebrate species composition significantly differed among different mangrove zones. The results also showed the seasonal variations. The findings of diversity indices illustrated that deltaic zone had the highest abundance and diversity, while the coastal zone showed the lowest values among the three zones. Taken together, the observations demonstrated that the different hydrological conditions, temperature, salinity and sediment texture were the main factors determining dispersion of benthic faunal assemblages among different mangrove habitats at Hara Biosphere Reserve. There is a need to consider such variables in ecological studies to understand differences of macrofaunal diversities in these complex habitats.

Long-term (1998 vs. 2010) large-scale comparison of soft-bottom benthic macrofauna composition in the Gulf of Lions, NW Mediterranean Sea

We achieved a long term (i.e., 1998 vs. 2010) large scale (i.e., whole Gulf of Lions) study of benthic macrofauna composition in the Gulf of Lions based on the resampling of 91 stations located along 21 inshore-offshore transects. Results show that the 3 main benthic communities identified in 1998 were still present in 2010 although their composition changed. Using only year and station of sampling we found a significant space-time interaction explaining changes in macrofaunal community composition, and, in this study, stations differ primarily in terms of depth and distance to the Rhône river mouth. Temporal changes in benthic macrofauna composition were clearly most important at shallow stations (i.e., in the Littoral Fine Sand community) than at deep ones (i.e., Terrigenous Coastal Mud community). These results are in good agreement with the current paradigm according to which climatic oscillations such as NAO (North Atlantic Oscillation) and WeMO (Western Mediterranean Oscillation) are indirectly (i.e., through changes in the frequency of occurrence and the intensity of storms) controlling benthic macrofauna composition in the Gulf of Lions. This hypothesis is further supported by a meta-analysis of changes in the average and maximal yearly abundances of the polychaete Ditrupa arietina. At last, the spatial modelling of 1998 and 2010 benthic macrofauna compositions both suggested a significant effect of Rhône River inputs on the spatial distribution of benthic macrofauna in the Gulf of Lions.

Spatiotemporal changes in surface sediment characteristics and benthic macrofauna composition off the Rhône River in relation to its hydrological regime

The consequences of changes in the water flow of the Rhône River on surface sediment characteristics and benthic macrofauna composition were assessed within 3 distinct areas: (1) the delta front, (2) the prodelta, and (3) the distal zone. Five stations were sampled during or closely after: (1) an oceanic flood (April 2007), (2) a generalized flood (May 2008), (3) a Cevenol flood (December 2008), and (4) a dry period (July 2011). Measurements of sediment characteristics included granulometry (D0.5), bulk descriptors of sedimentary organics (OC, TN and THAA), descriptors of labile components of sedimentary organics (chloropigments, EHAA), and both descriptors of origin (Chl-b/Chl-a, C/N) and lability (Chl-a/(Chl-a+Phaeo-a), EHAA/THAA) of sedimentary organics. Sediment Profile Images were collected during April 2007, May 2008 and July 2011. Temporal changes in both sedimentary organics and benthic macrofauna were more important in the delta front and the prodelta than in the distal zone. Bulk characteristics of sedimentary organics presented decreasing inshore/offshore gradients during both April 2007 and July 2011 but not during May and December 2008. There were significant temporal changes in EHAA/THAA at all stations. Changes in benthic macrofauna composition differed between: (1) the delta front and the prodelta, and (2) the distal zone. In the former area, the dry period was associated with establishing a mature community characterized by high abundances and species richness. The best description of spatiotemporal changes in benthic macrofauna composition by surface sediment characteristics was obtained using D0.5, Chl-b/Chl-a, Chl-a/(Chl-a+Phaeo-a) and EHAA, which supports the role of the quality of sedimentary organics in controlling benthic macrofauna composition.

Distinctly variable mudscapes: Distribution gradients of intertidal macrofauna across the Dutch Wadden Sea

The Wadden Sea is a shallow coastal region, with a large area of sedimentary tidal flats that extends from The Netherlands to Denmark and has been declared a site of international importance in the Dutch and German parts (Ramsar status and UNESCO World Heritage Site). Benthic macrofauna are central to the ecosystem functioning of this area, as they recycle nutrients, decompose organic matter and are an important food source for many secondary consumers, like fish and waterbirds. Due to the environmental gradients characteristic of estuarine systems, it is expected that changes in assemblage composition will be observed across the physical and environmental gradients of the Wadden Sea. First, we explored the spatial variation in assemblage composition of benthic macrofauna across the intertidal part of the Dutch Wadden Sea using 3years of biomass data. Then, we identified the relative importance of six environmental variables for explaining and predicting changes in assemblage composition across the intertidal areas of the Wadden Sea using generalised dissimilarity modelling (GDM). In accordance with the environmental gradients across this system, the biomass contributed by a few common species differed from west to east and were distinct in the Dollard. In the west, bivalves Mya arenaria, Cerastoderma edule and Ensis directus contributed a relatively large and equal share of the total biomass, whereas C. edule contributed the sole largest share of the total biomass towards the east. The polychaete Alitta succinea became a large share of the total biomass in the upper Ems and in the Dollard estuary, but contributed little elsewhere. Similar to the observed differences in species composition, the spatial patterns in assemblage composition, as predicted by the GDM models, identified the Dollard as distinct and that the prevalence of assemblage types in the west differed to the east. Median grain size, followed by microphytobenthic biomass, and exposure time were the most important variables describing differences in assemblage composition. That the Wadden Sea forms a heterogeneous landscape where assemblage composition varies across multiple gradients has repercussions for management and monitoring.

Remediation of Contaminated Marine Sediment Using Thin-Layer Capping with Activated Carbon—A Field Experiment in Trondheim Harbor, Norway

In situ amendment of contaminated sediments using activated carbon (AC) is a recent remediation technique, where the strong sorption of contaminants to added AC reduces their release from sediments and uptake into organisms. The current study describes a marine underwater field pilot study in Trondheim harbor, Norway, in which powdered AC alone or in combination with sand or clay was tested as a thin-layer capping material for polycyclic aromatic hydrocarbon (PAH)-contaminated sediment. Several novel elements were included, such as measuring PAH fluxes, no active mixing of AC into the sediment, and the testing of new manners of placing a thin AC cap on sediment, such as AC+clay and AC+sand combinations. Innovative chemical and biological monitoring methods were deployed to test capping effectiveness. In situ sediment-to-water PAH fluxes were measured using recently developed benthic flux chambers. Compared to the reference field, AC capping reduced fluxes by a factor of 2-10. Pore water PAH concentration profiles were measured in situ using a new passive sampler technique, and yielded a reduction factor of 2-3 compared to the reference field. The benthic macrofauna composition and biodiversity were affected by the AC amendments, AC + clay having a lower impact on the benthic taxa than AC-only or AC + sand. In addition, AC + clay gave the highest AC recoveries (60% vs 30% for AC-only and AC + sand) and strongest reductions in sediment-to-water PAH fluxes and porewater concentrations. Thus, application of an AC-clay mixture is recommended as the optimal choice of the currently tested thin-layer capping methods for PAHs, and more research on optimizing its implementation is needed.

Comparison of ecological quality indices based on benthic macrofauna and sediment profile images: A case study along an organic enrichment gradient off the Rhône River

Several studies have shown the occurrence of major discrepancies between the most commonly used benthic biotic indices within the EU Water Framework Directive. Such studies have however failed to assess, which indices perform best because of the lack of an independent assessment of benthic habitat ecological quality. The present study aimed at filling this gap by comparing the use of several biotic indices derived from benthic macrofauna composition and one index derived from sediment profile imagery, based on the sampling of 16 stations along a gradient of sedimentary organic carbon concentrations (OC) in front of the mouth of the Rhône River. Five biotic benthic macrofauna indices (BQI, BQI ES, AMBI, M-AMBI, and W) were computed together with the benthic habitat quality (BHQ) index, which is derived from sediment profile images (SPI). All sampled stations but one belonged to the same community as affected by a gradient of organic enrichment. BQI, BQI ES and BHQ correlated significantly between each other's and with OC. Conversely, AMBI and W did not correlate with either BHQ or OC. As organic enrichment is known to constitute a major source of disturbance, this suggests that BQI and BQI ES performed better than AMBI, M-AMBI and W in assessing the ecological quality of soft sediments in the studied area. Discrepancies between BQI and AMBI derived indices are discussed based on differences in the sensitivity/tolerance levels attributed to most dominant species by these two indices.

Temporal trends in benthic macrofauna composition in response to seasonal variation in a tropical coastal lagoon, Celestun, Gulf of Mexico

Aquatic habitats in some tropical coastal environments can change seasonally, causing changes in the community structure of the benthic macrofauna. A tropical coastal lagoon, the Celestun lagoon, on the north-west Yucatan peninsula, was sampled seasonally and faunal, water and sediment data were compared with conditions during the 1994–1995 weather cycle across a grid of 12 sites distributed along the lagoon’s salinity gradient. Habitat variation was expressed as physical factors associated with the water column (e.g. salinity) and bottom sediments (e.g. interstitial salinity, texture), whereas the benthic community response was assessed through changes in species composition, diversity and dominance. Taxonomic dominance varied according to changes in seasonal habitat characteristics. During the season of strong northerly winds (‘nortes’), molluscs dominated and polychaetes almost disappeared. Polychaetes then recovered during the dry season, becoming as common as crustaceans and molluscs. Finally, during the rainy season, polychaetes became the dominant group and molluscs declined. A conceptual model summarising the community structure changes associated with key physical and biotic factors is proposed. The results indicate that the benthic community of the Celestun lagoon is a resilient one, largely driven by natural weather variability in this tropical ecosystem to a greater extent than previously suggested.

How biodiversity affects ecosystem functioning: roles of infaunal species richness, identity and density in the marine benthos

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 311:263-271 (2006) - doi:10.3354/meps311263 How biodiversity affects ecosystem functioning: roles of infaunal species richness, identity and density in the marine benthos Elena N. Ieno1,3, Martin Solan1,*, Paul Batty2, Graham J. Pierce1 1Oceanlab, University of Aberdeen, Main Street, Newburgh, Aberdeenshire AB41 6AA, UK 2The Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, UK 3Present address: Highland Statistics, 6 Laverock Road, Newburgh, Aberdeenshire AB41 6FN, UK *Corresponding author. Email: m.solan@abdn.ac.uk ABSTRACT: The extent to which changes in biodiversity are causally linked to key ecosystem processes is a primary focus of contemporary ecological research. Highly controlled manipulative experiments have revealed significant and positive effects of increased diversity on ecosystem functioning, but uncertainties in experimental design have made it difficult to determine whether such effects are related to the number of species or to effects associated with species identity and density. Using infaunal marine invertebrates, we established 2 parallel laboratory experiments to examine the hypothesis that changes in the composition of benthic macrofauna alter the biogeochemistry of coastal intertidal mudflats. Our study identified clear effects of increased infaunal species diversity on nutrient generation. However, significant species identity and density effects underpin the observed response, reflecting species-specific traits associated with bioturbation. Post-hoc examination of our conclusions using power analysis revealed that, given our experimental design, the probability of finding a correct significant effect, the minimum detectable difference necessary to detect a significant effect, and the minimum number of replicates necessary in order to achieve an acceptable power, all differed between species. Our study has important implications for the design of biodiversity–ecosystem function experiments because the disparity between the contributions that individual species make to ecosystem function demands the use of different levels of replication for each species within an experiment. KEY WORDS: Biodiversity · Ecosystem function · Species richness · Experimental design · Nutrients · Bioturbation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 311. Online publication date: April 13, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Benthic macro-invertebrate community composition within a mangrove/seagrass estuary in northern New Zealand

In the tropics and sub-tropics, estuarine environments with mangrove and seagrass habitats provide important structures and resources for diverse communities of benthic organisms. However, temperate estuarine habitats, especially in mangrove areas, may differ significantly in their community associations and interactions. The community composition of benthic macro-fauna was investigated within temperate Matapouri Estuary, northern New Zealand. The density and distribution of fauna were sampled within six distinctive habitats (mangrove stands, pneumatophore zones, Zostera beds, channels, banks, and sand flats), within four sampling events between December 2002 and September 2003. Each type of habitat was replicated seven times within different locations in the estuary. Counts of all infauna and epifauna within four replicate cores were recorded from each habitat and location. Multidimensional scaling plots were used to identify differences in structure and composition of assemblages among habitats and locations within each sampling event. Results from these benthic samples indicate that Matapouri Estuary has a high overall biodiversity, with distinctive faunal assemblages found within different habitats, and some seasonal variations also apparent. In terms of both number of individuals and taxa per unit area, seagrass beds had the highest numbers and mangrove areas had the lowest numbers, with all other habitats in between. Some locations were found to support a high diversity of organisms across habitats, while other locations had high densities of a few species only. Several physical and biological differences between tropical/sub-tropical and New Zealand's temperate mangrove habitats are put forth as potential reasons for the lower density and diversity of the benthic component observed herein. Further ongoing studies aim to elucidate the structure and interactions within food webs in this estuarine ecosystem.

Composition and Abundance of Benthic Macrofauna of a Tropical Sea-Grass Bed in North Queensland, Australia

The aims of this study were to characterize the functional composition of benthic macrofauna of a tropical sea-grass bed and to determine temporal variations in abundance of benthic macrofauna in relation to environmental factors such as sea-grass biomass, temperature, salinity, and sediment type. Benthic macrofaunal composition and abundance were investigated by core sampler during April 1999, October 1999, March 2000, and August 2000 at three stations within a sea-grass bed at Cockle Bay in North Queensland, Australia. A total of 110 species of benthic macrofauna was collected. Polychaetes were the most abundant group (37 species; 52% of total macrofaunal numbers; 47% of biomass) followed by amphipods (27 species; 35% of total numbers). Decapods were also important, with 28 species contributing 31% of total macrofaunal biomass. Other miscellaneous groups were tanaids, isopods, and ophiuroids. Most amphipods (65%) and decapods (90%) were epifaunal, but polychaetes were equally represented by epifauna and infauna. Temporal variation in both species composition and abundance was large: the peak number of benthic macrofauna occurred in April 1999 and March 2000, and biomass was highest in April 1999. Benthic macrofauna numbers as well as biomass were lowest in August 2000. These temporal patterns of abundance of benthic macrofauna appeared to correlate closely with temporal variation of sea-grass biomass. In addition, the factors of life cycle and predation by common fish species may be indirectly associated with these patterns of macrofaunal abundance.

Changes in the Diet of Demersal Fish due to Eutrophication-Induced Hypoxia in the Kattegat, Sweden

The diets of five dominant bottom-feeding fish species, Atlantic cod (Gadus morhua), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), dab (Limanda limanda), and American plaice (Hippoglossoides platessoides), were analysed during spring and autumn between May 1984 and April 1988 in the southeast Kattegat. A general long-term change in the diet of bottom-feeding fish in the Kattegat has taken place since the beginning of the century and, for some of the species, the feeding pattern was different from that in adjacent areas. The observed dietary shift appeared to be due to changes in species composition of benthic macrofauna. Prey species favored by increased organic enrichment were dominant in the diet. Several infaunal species increased in dietary importance during recent hypoxia. In contrast, during hypoxia, a reduction of epibenthic crustaceans was observed in the fish diet. This study emphasizes the potential effects of organic enrichment and hypoxia (due to eutrophication) on trophic interactions in marine benthic communities. Repeated stress from hypoxia might favor small-sized prey species with a short life cycle, which would in turn favor small-sized fishes. Thus, altered food resources and the direct effects of hypoxia might result in shift in dominance among demersal fish species.