Benthic Macroinvertebrate Species Research Articles

An assessment of a tropical urban stream using benthic macroinvertebrates as a bio-indicator in Muara Angke, Jakarta, Indonesia

Kelly C, Mitrasetia T, Sugardjito J. 2017. An assessment of a tropical urban stream using benthic macroinvertebrates as a bio-indicator in Muara Angke, Jakarta, Indonesia. Bonorowo Wetlands 1: 65-73. A preliminary study was conducted on the populations, density and distributions of benthic macroinvertebrate species along the course of the Ciliwung/Angke River, Jakarta. The selected river section is highly urbanized and heavily polluted, and five study sites were selected along its course to assess the health of the river ecosystem. Benthic macroinvertebrates are used as a bio-indicator for evaluation of ecosystem health. Their different pollution sensitivities, wide distribution and relatively sedentary lives make them useful candidates for this role. The focal point of the study is the MuaraAngke mangrove forest and wetland, a small remnant wetland at the mouth of the river in Jakarta Metropolitan. A comparison is drawn between the different study sites to assess the health and potential utility of this unique habitat. Despite several intense pressures resulting from the highly urbanized surroundings, and the mangrove's position at the mouth of the river where pollution accumulation would be highest, the data collected from this site showed a macroinvertebrate population dominated by pollution -sensitive taxa, suggesting the mangrove itself continues to provide significant ecosystem services in water -purification.

Benthic macroinvertebrates and degradation of phytomass as indicators of ecosystem functions in flooded rice cropping

Abstract: The objective of this work was to evaluate the ecosystem functions of a natural wetland and of artificially flooded rice areas, managed under organic and conventional systems, by phytomass degradation and by the colonization of this material by benthic macroinvertebrates. The experiment was carried out in a natural wetland area, and in two flooded rice areas managed under organic and conventional systems. Twenty-five decomposition bags filled with 10 g of dry vegetation were installed in each site. At 14, 28, 42, 56, and 70 days after the beginning of the experiment, five bags from each site were collected. Macroinvertebrates were identified and classified by functional trophic group. The number of species of benthic macroinvertebrates increased: natural wetland > organic system > conventional system. The Chironomidae group was present in all areas, confirming its food plasticity and adaptability to different substrates and environmental stress situations. The Amphipoda group was present only in the artificially flooded rice area, and the Acari, only in the natural wetland. The diversity of species in the natural wetland area was higher than in the artificially flooded rice area. Nutrient cycling, provided by phytomass decomposition, is affected by the management system, and the delay in this process causes a reduction of the ecosystem functions in the conventional system.

Do Mining Activities Significantly Affect Feeding Behavior of Freshwater Benthic Macroinvertebrates? A Case Study in South Sardinia (Italy)

We investigated the cascading effects of chemical contaminants on alder leaf detritus quality and the exploitation of this feeding resource by benthic macroinvertebrates (isopods, gastropods, and mayfly nymphs). Trophic behavior and energetics of benthic macroinvertebrates were used to evaluate the effects of contaminants on detritus exploitation. A two-way factorial nested experimental design was used to statistically quantify how leaf detritus origin (polluted and unpolluted streams) and the pollution level of the site selected for microbial conditioning of the detritus could affect the feeding resource quality for aquatic benthic macroinvertebrates, as measured by their trophic behavior (i.e. food selection) and exploitation (i.e. food ingestion). Alder leaves collected from a polluted stream in a former mining area (South-Sardinia, Italy) had Cd, Pb, and Zn concentrations up to 10 times that of leaves collected from an unpolluted stream. When benthic macroinvertebrates were given the option to choose, they all selected leaves from the unpolluted stream and/or those conditioned in the unpolluted stream. Ingestion rates were also significantly affected by both considered factors: leaf origin and conditioning. In addition, synergistic effects strongly increased the chemical contaminant stress on the leaf detritus quality. These results show that the terrestrial component of land–water ecotones affected by mining can be a relevant indirect pathway of chemical stress to benthic macroinvertebrate species.

Microplastics en route: Field measurements in the Dutch river delta and Amsterdam canals, wastewater treatment plants, North Sea sediments and biota

Environmental contamination by plastic particles, also known as ‘microplastics’, brings synthetic materials that are non-degradable and biologically incompatible into contact with ecosystems. In this paper we present concentration data for this emerging contaminant in wastewater treatment plants (WWTPs) and freshwater and marine systems, reflecting the routes via which these particles can travel and the ecosystems they potentially impact along their path. Raw sewage influents, effluents and sewage sludge from seven municipal WWTPs in the Netherlands contained mean particle concentrations of 68–910L−1, 51–81L−1 and 510–760kg−1 wet weight (ww), respectively (particle sizes between 10 and 5000μm). Even after treatment, wastewater constitutes a source of microplastic pollution of surface waters, and via biosolids applications in farming and forestry, plastic retained in sewage sludge can be transferred to terrestrial environments. The WWTPs investigated here had a mean microplastics retention efficiency of 72% (s.d. 61%) in the sewage sludge. In the receiving waters of treated and untreated wastewaters, we detected high microplastic levels in riverine suspended particulate matter (1400–4900kg−1 dry weight (dw)) from the Rhine and Meuse rivers. Amsterdam canal water sampled at different urban locations contained microplastic concentrations (48–187L−1), similar to those observed in wastewater that is emitted from sewage treatment facilities in the area. At least partial settling of the particles occurs in freshwater as well, as indicated by microplastics in urban canal sediments (<68 to 10,500particleskg−1dw). Microplastics in suspension in the water column have the potential to be discharged into the sea with other riverine suspended particulates. We report microplastic concentrations from 100 up to 3600particleskg−1 dry sediment collected at 15 locations along the Dutch North Sea coast. The high microplastic enrichment in marine sediments compared to most literature data for seawater at the surface supports the hypothesis of a seabed sink for these materials. Marine species are heavily exposed to plastic particles. Body residues between 10 and 100particlesg−1dw were measured in benthic macroinvertebrate species inhabiting the Dutch North Sea coast: filter-feeding mussels and oysters (species for human consumption) as well as other consumers in the marine food chain.

Benthic macroinvertebrate of Adıgüzel Reservoir (Denizli, Turkey)

In order to determine the benthic macro-invertebrates of Adiguzel Reservoir, samplings were performed between January 2007 and December 2007 at four stations in dam lake and littoral zone. During the samplings, an Ekman Grab was used in those stations located in dam lake and 180 µ mesh sized hand nets were used in coastal samplings. Collected material were fixed in 4% formolin solution in field and then washed and sorted, identified and counted in laboratory.As a result of the study, totaly six species were determined. Of them, three belong to Diptera ( Chironomus tentans, Polypedilum nubeculosum, Procladius (Holotanypus) sp. ), two to Malacostraca (Paramysis kosswigi, Pontogammarus robustoides ) and one belongs to Oligochaeta ( Nais pardalis ). All of the determined species were firstly reported from the locality. The profundal zone of the Adiguzel Reservoir was poor in terms of productivity and the average chironomid density was 17 ind/m2. The remaining benthic macroinvertebrate species determined in this study were sampled from the littoral zone of the dam lake. Keywords: Benthic macroinvertebrate, Adiguzel Reservoir, Denizli, Turkey

The habitat type and trophic state determine benthic macroinvertebrate communities in lowland shallow lakes of China

&lt;p&gt;Benthic macroinvertebrates play important roles in shallow lake ecosystems. Several studies based on qualitative comparisons of the amount of macrophytes were carried out to relate benthic macroinvertebrate assemblages to habitat conditions in shallow lakes. Our main aim was to analyze the effects of habitat type and trophic state on taxonomic composition and abundance of benthic macroinvertebrates in lowland shallow lakes based on quantitative classification of habitat types. The benthic macroinvertebrate assemblages were investigated in eight shallow lakes of eastern China in four seasons. A total of 33 species was collected from these lakes, including four Oligochaeta, eight Chironomidae, eight Gastropoda, four Bivalvia and nine other miscellaneous species. According to the ratio of the dry weight of macrophytes to the dry weight of phytoplankton, the study lakes were separated into three lake types; macrophyte-dominated, transitional, and algae-dominated regions. The total abundance of macroinvertebrates was significantly higher in the group of algae-dominated regions than in the macrophyte-dominated regions. Scrapers had the highest abundance in the macrophyte-dominated regions. Univariate and multivariate analyses results showed that abundance, biomass and characteristic species of benthic macroinvertebrates were affected by their habitat types. The abundance and biomass of macroinvertebrates showed significant positive correlations with the trophic state index (TSI). TSI and turbidity were significantly correlated with DC1 (Axis 1 of detrended correspondence analysis), while Chlorophyll &lt;em&gt;a&lt;/em&gt; and the ratio of the dry weight of macrophytes to the dry weight of phytoplankton were significantly correlated with DC2. The findings indicated that the habitat type and trophic state were the key factors determining the structure of macroinvertebrate assemblages in lowland shallow lakes. Our study was one of the few studies that had demonstrated the distinct influence of habitat type on macroinvertebrate assemblages in shallow lakes according to the ratio of the dry weight of macrophytes to the dry weight of phytoplankton.&lt;/p&gt;

Effects of engineered application of Eichhornia crassipes on the benthic macroinvertebrate diversity in Lake Dianchi, an ultra-eutrophic lake in China.

An ecological engineering project with confined growth of 1.5km(2) of Eichhornia crassipes was implemented to remove pollutants in Lake Dianchi. To assess the ecological effects of this project on benthic macroinvertebrate assemblages, a 1-year investigation at the areas inside and outside E. crassipes mats was conducted from May 2013 to May 2014. All the 10 sampling sites in the areas were grouped into two statistically significant clusters mainly corresponding to inside and outside E. crassipes mat areas (EMAs), by clustering analysis. E. crassipes reduced the densities of pollution indicator taxa (e.g., Oligochaeta and Chironomidae larvae); thus, the total densities of benthic macroinvertebrates at the area inside EMAs (mean 328.2ind./m(2)) were slightly lower than that at the area outside EMAs (mean 505.6ind./m(2)). Four functional feeding groups including 38 species of benthic macroinvertebrates were collected at the area inside EMAs, while only three functional feeding groups containing 17 species were collected at the area outside EMAs. The biodiversity indices (Shannon-Weiner, Margalef, Simpson, and Peilou indices) and K-dominance curves also showed higher diversity of benthic macroinvertebrates at the area inside EMAs than at the area outside EMAs. These results suggested that a certain scale of engineering application of E. crassipes was beneficial to benthic macroinvertebrate communities in the ultra-eutrophic Lake Dianchi and it could be used as a pioneer species in ultra-eutrophic lake for pollutant removal.

Competition in slow motion: the unusual case of benthic marine communities in the wake of the end‐Permian mass extinction

AbstractChanges of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end‐Permian mass extinction, which is associated with the microbial limestone facies of the earliestTriassic ofSouthChina. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new speciesAstartella?stefaniae(Bivalvia) andEucochlis obliquecostata(Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10–100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the long‐term effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end‐Permian mass extinction. We suggest that these non‐actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatestPhanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.

Preliminary limnological survey of Ori stream, Iwo, Osun State, Nigeria

Ori stream (one of the tributaries of River Oba, Iwo, Osun State, Nigeria) was studied from October to December 2013 with the aim of providing baseline information on its water quality, phytoplankton primary productivity and invertebrate faunal composition. Plankton samples were collected by towing plankton net over a 2 metres horizontal distance, while benthic macroinvertebrate samples were collected by kick-sampling technique. Hydrological and some physico-chemical variables were determined in-situ , and water samples collected for further physico-chemical analyses in the laboratory. A total of 17 phytoplankton species, seven species of zooplankton and eight species of benthic macroinvertebrates were recorded. The upper reach of the stream was the most polluted with the presence of biological indicators of poor water quality, while the lower reach recorded some biological indicators of good water quality. Although the upper reach recorded the highest gross primary productivity, the highest net primary productivity was recorded at the stream’s lower reach. Water quality typically decreased from the upper reach of the stream towards the middle reach but later picked up at the lower reach before discharging into River Oba. The physico-chemical and biotic nature of the different reaches were a reflection of human activities in and around the stream. Keywords : Benthic macroinvertebrates, conservation, headwater stream, plankton; primary productivity, water quality.

A comparison of modelled and actual distributions of eleven benthic macroinvertebrate species in a Central European mountain catchment

Species distribution Modelling (SDM) constitutes a useful tool to predict the distribution of freshwater species based on selected habitat variables. Model performance (goodness-of-fit) expressed as coefficient of determination is straightforward to judge on SDM quality but does not sufficiently address predictive success. Hence, predictive performance (e.g. AUC) accounts for the correctness of predicted species occurrences. In this study, we compared the model and predictive performance of SDMs on eleven macroinvertebrate taxa in a mountain catchment, with emphasis on species prevalence. SDMs were based on two regression methods using broad-scale environmental predictors (land use, instream habitat quality). We applied a cross-validation and a field validation approach using newly sampled field data. Opposed to other species, SDMs showed acceptable performance (pseudo-R2 > 0.3) for the stonefly Dinocras cephalotes and the caddisflies Silo piceus and Silo pallipes. Model performance was neither positively nor linearly correlated with predictive accuracy. The comparison of cross- and field validation revealed an overestimation of the discriminatory power of cross-validated models. SDMs of less prevalent species tend to over-predict absences rather than presences. Consequently, model performance is decoupled from predictive performance. The validation results suggest the use of new field data providing a more reliable benchmark for SDM assessment.

Spatio-temporal characteristics of the fatty acid compositions of two macrobenthos (Nuttallia olivacea and Hediste sp.) in the Nanakita River estuary, Japan

This study examined species-specific, dietary responses of two benthic macroinvertebrate species, Nuttllia olivacea and Hediste sp., to spatial and seasonal variations of resource composition in an estuarine tidal flat system of north-eastern Japan. This study measured fatty acid (FA) composition of sedimentary organic matter and macroinvertebrate tissue to estimate relative contributions of organic matter originating from different sources. N. olivacea and Hediste sp. are predominated in macrobenthos communities of sandy and muddy sediments in the studied estuary, respectively. The total FA of sedimentary organic matter was significantly related positively to the total organic carbon (TOC) content of sediment. FAs of diatom, bacteria, and terrestrial–plant origins were found higher values in the sediments with higher TOC. The dietary composition of N. olivacea showed both spatial and seasonal variations, but was consistently linked with diatom, bacteria and dinoflagellates in the sediments. Meanwhile, the FA composition of Hediste sp. demonstrated that the diets of this species depended heavily on diatom, bacteria and terrestrial plant. From these results it was revealed that Hediste sp. was more tightly linked with sedimentary organic matter composition compared with N. olivacea. This result indicates that Hediste sp. has a euryphagic diet and is possible to feed on sedimentary organic matter of various sources in natural environments. Both macroinvertebrate species showed different characteristics in terms of using of food resources and its spatial and seasonal variation. It is considered that the difference in feeding dietary habit of macroinvertebrates is one of the important factors which decide the sediment suitability for macrobenthos.

와이블 분포함수를 이용한 저서성 대형무척추동물의 종수-조사면적 관계 해석

The relationship between the number of benthic macroinvertebrate species and the accumulated survey area were investigated in a clean stream and an impaired stream of Korea. Five models to characterize species-area functions were compared, and the Weibull model fitted species-area data well. The other models (Arrhenius, Romell-Gleason, Kylin, Lognormal model) had small or notable bias. The maximum number of species and half-saturation area derived from the Weibull model may be used as the indicators of the carrying capacity and the habitat complexity respectively.

Studying the movement behavior of benthic macroinvertebrates with automated video tracking.

Quantifying and understanding movement is critical for a wide range of questions in basic and applied ecology. Movement ecology is also fostered by technological advances that allow automated tracking for a wide range of animal species. However, for aquatic macroinvertebrates, such detailed methods do not yet exist. We developed a video tracking method for two different species of benthic macroinvertebrates, the crawling isopod Asellus aquaticus and the swimming fresh water amphipod Gammarus pulex. We tested the effects of different light sources and marking techniques on their movement behavior to establish the possibilities and limitations of the experimental protocol and to ensure that the basic handling of test specimens would not bias conclusions drawn from movement path analyses. To demonstrate the versatility of our method, we studied the influence of varying population densities on different movement parameters related to resting behavior, directionality, and step lengths. We found that our method allows studying species with different modes of dispersal and under different conditions. For example, we found that gammarids spend more time moving at higher population densities, while asellids rest more under similar conditions. At the same time, in response to higher densities, gammarids mostly decreased average step lengths, whereas asellids did not. Gammarids, however, were also more sensitive to general handling and marking than asellids. Our protocol for marking and video tracking can be easily adopted for other species of aquatic macroinvertebrates or testing conditions, for example, presence or absence of food sources, shelter, or predator cues. Nevertheless, limitations with regard to the marking protocol, material, and a species’ physical build need to be considered and tested before a wider application, particularly for swimming species. Data obtained with this approach can deepen the understanding of population dynamics on larger spatial scales and of the effects of different management strategies on a species’ dispersal potential.

Influence of habitat structure and environmental regime on spatial distribution patterns of macroinvertebrate assemblages associated with seagrass beds in a southern Gulf of Mexico coastal lagoon

AbstractSeagrass meadows are important for their ecological functions and ecosystem services, including habitat and shelter for a high diversity of species. The present study aims to assess the spatial distribution patterns of macroinvertebrate assemblages associated with Thalassia testudinum beds in a tropical coastal lagoon of the southern Gulf of Mexico. Environmental variables and core samples were taken from three shallow beds with different degrees of exposure to wind-driven waves: protected, exposed and semi-exposed. A total of 40 benthic macroinvertebrate species were recorded, molluscs being the most important group in terms of diversity and abundance. The highest species richness was recorded at the semi-exposed site (31 species), while the highest abundance was at the exposed site (5207 ind. m−2). Despite inter-site variations in environmental variables and physical descriptors of seagrass (seagrass biomass, shoot density, leaf length), the species richness and abundance of macroinvertebrates c...

Influence of habitat structure and environmental regime on spatial distribution patterns of macroinvertebrate assemblages associated with seagrass beds in a southern Gulf of Mexico coastal lagoon

Seagrass meadows are important for their ecological functions and ecosystem services, including habitat and shelter for a high diversity of species. The present study aims to assess the spatial distribution patterns of macroinvertebrate assemblages associated with Thalassia testudinum beds in a tropical coastal lagoon of the southern Gulf of Mexico. Environmental variables and core samples were taken from three shallow beds with different degrees of exposure to wind-driven waves: protected, exposed and semi-exposed. A total of 40 benthic macroinvertebrate species were recorded, molluscs being the most important group in terms of diversity and abundance. The highest species richness was recorded at the semi-exposed site (31 species), while the highest abundance was at the exposed site (5207 ind. m−2). Despite inter-site variations in environmental variables and physical descriptors of seagrass (seagrass biomass, shoot density, leaf length), the species richness and abundance of macroinvertebrates correlated only with seagrass biomass. Multivariate analyses showed a clear separation of macroinvertebrate assemblages into two main groups according to the degree of exposure of the sites as exposed/semi-exposed or protected. It was also determined that seagrass biomass, hydrodynamism, sedimentation/resuspension rates and the proportion of coarse particles in the sediment appear to be the variables that best explain the differences between sites. These findings support the importance of including sites with different degrees of exposure in assessing the biodiversity of seagrass beds at the landscape scale, because species composition, species richness and the abundance of associated fauna may vary considerably between sites within the same coastal region according to a combination of biotic and abiotic factors.

Effect of Roxithromycin on the Activity of Enzyme ERND in the Kidney of Mollusk (&lt;i&gt;Cipangopaludina&lt;/i&gt;&lt;i&gt; chinensis&lt;/i&gt;)

Cipangopaludina chinensis which is a species of benthic macroinvertebrates was exposed to roxithromycin, and tested the erythromycin N-demethylase (ERND) of kidney, then explored the effect of roxithromycin on the biochemical indicator of C.chinensis. The results showed that roxithromycin had effect on the activity of ERND in the kidney of C.chinensis and the overall trend was promoting at the beginning then suppressing at the end, but the differences of the influence caused by different concentrations of roxithromycin was not obvious. In addition, it appeared from the survival condition of control group and experimental group, roxithromycin which is a kind of antibiotic, had no lethal effect on C.chinensis. But the concentration of roxithromycin which is more than 250 times, 500 times and 750 times of the environment used in this experiment had significant influence on the enzyme activity of the ERND in the kidney of C.chinensis.

Understanding the relationships among phytoplankton, benthic macroinvertebrates, and water quality variables in peri-urban river systems.

In this article, using the Hawkesbury-Nepean River as a case study, the spatial and temporal trends of water quality variables over three sampling surveys in a peri-urban situation are examined for their effect on benthic macroinvertebrate communities and phytoplankton communities and whether phytoplankton and benthic macroinvertebrate species can be used as indicators for river health assessment. For this, the authors monitored the spatial and temporal difference of 10 water quality parameters: temperature, turbidity, pH, dissolved oxygen, electrical conductivity, oxidation reduction potential, total nitrogen, total phosphorus, manganese, and suspended solids. The variability in water quality parameters clearly indicated a complex pattern, depending on the season (interaction p = 0.001), which highlighted how the river condition is stressed at multiple points as a result of anthropogenic effects. In particular, the downstream locations indicated an accumulation of nutrients, the presence of increased sediments, and phytoplankton related variables such as total counts, bio-volumes, chlorophyll-a, and total phosphorus. The patterns of phytoplankton communities varied in a complex way depending on the season (interaction p = 0.001). Abundances of phytoplankton were also found in low concentrations where the water column is not severely disturbed by flow and tide. However, when the water clarity drops resulting from tidal cycles, inflows from tributaries, and intense boating activities, the phytoplankton abundances also increased considerably. On the other hand, benthic macroinvertebrates compositions were significantly different between locations (p = 0.001) with increased abundances associated with upstream sites. Aphanocapsa holsatica and chironomid larvae appeared as the important indicators for upstream and downstream site differences in water quality. Water temperature influenced the phytoplankton community pattern (ρ(w) = 0.408), whereas pH influenced the benthic macroinvertebrate community pattern (ρ(w) = 0.437). The findings of this study provide valuable insights into the interactions of water quality parameters on biotic assemblages and to the extent that benthic macroinvertebrates and phytoplankton assemblages are suitable as indicators for monitoring and assessing peri-urban river health.

ASSESSMENT OF BENTHIC MACRO-INVERTEBRATE FAUNA IN TWO CONTIGUOUS COASTAL WATER BODIES WITHIN BARRIER LAGOON COMPLEX, WESTERN NIGERIA

As a means of assessing ecological status in the westernmost part of the Barrier Lagoon Complex in western Nigeria, compositions and distributions of benthic macro-invertebrate fauna were studied in two contiguous water bodies within the complex, Badagry Creek and Ologe Lagoon. Samples of benthic macro fauna were collected from five stations in each of the two water bodies and analysed using standard methods both in the wet (June and September 2011) and dry (February and April 2012) seasons. A total of eighteen benthic macro-invertebrate species belonging to classes Bivalvia, Gastropoda, Crustacea and Polychaeta were recorded in Badagry Creek while from Ologe Lagoon, a total of thirteen species were recorded belonging to Classes Bivalvia, Gastropoda and Oligochaeta. Organic pollution tolerant species of polychaetes and oligochaetes were recorded in the two water bodies only at the stations close to municipal wastes discharge points. Higher macro-invertebrate abundance levels were recorded from the two water bodies in the dry than wet season. Badagry Creek recorded higher macro-invertebrate abundance (589 and 632 in wet and dry seasons respectively) and diversity indices values than Ologe Lagoon (with 92 and 404 abundance values during wet and dry season respectively). Relatively very low benthic macro-invertebrate abundance and taxa number were recorded from the stations close to sand mining activities especially in Ologe Lagoon. The implications of the anthropogenic activities on the benthic macro-fauna in relation to sustainable management of the water bodies and resources therein are discussed.

The Benthic Macroinvertebrates of Kentucky Lake, a Mainstem Reservoir on the Tennessee River, U.S.A.

More than 230 species of benthic macroinvertebrates are recorded from Kentucky Lake, a major reservoir on the Tennessee River system, and compiled in an annotated list. Chironomidae (Diptera) and Unionidae (mussels) comprise more than 60% of the total taxa. Most species are restricted to shallow or marginal areas of the lake with only about 12 being common everywhere. The common species were similar to those found in both large and small reservoirs in the eastern United States. High disturbance regimes and sedimentation patterns are thought to control the similarities, limiting the communities to a small suite of adaptable species. This may reduce the usefulness of reservoirs in understanding climate change. A small number of invasive benthic species are well-established but appear to have had little affect on the rest of the benthic community. Invasive zooplankton and fish seem to have had little influence on the benthos, but the recent invasion of silver carp, Hypophthalmichthys molitrix (Valenciennes), may be a tipping point.

A model of life cycle, connectivity and population stability of benthic macro-invertebrates in the North Sea/Baltic Sea transition zone

The life cycle of many benthic macro-invertebrates is characterised by a planktonic life stage where larvae are transported by ocean currents and mixing and after some time they reach a stage where they settle onto the ocean bottom and, provided a suitable habitat is available, initiate their benthic life stage as juvenile organisms and complete their life cycle when they mature and spawn as adults. Such age-specific behaviour is in general difficult to include in large scale ocean models unless dispersal is considered on an individual basis, i.e. individual based model coupled with a Lagrangian description of the flow field. However, here we address this issue in an Eulerian framework and develop and apply a new life cycle and population dynamical model of benthic fauna and implement the model in a high-resolution three-dimensional circulation model of the North Sea/Baltic Sea transition zone. The model explicitly describes specific life stages of the population and considers the different processes affecting the organisms during their life cycle, e.g. spawning, dispersion and settling. The model considers different life stages of an idealised marine organism, representing a typical benthic macro-invertebrate species in the area. Populations of juvenile and adult benthic organisms are maintained by spawning, occurring regularly every spring, and subsequent settling of larvae. The pelagic larval stages are simulated by a larval concentration distribution function, i.e. discrete age-classes of the total larval concentration, and age-specific physiological processes, as the onset of their settling behaviour, is explicitly accounted for in the model. Model simulations show, in general, a large connectivity between habitats in the northern and southern part of the area but also that self-recruitment is sufficient to sustain the two populations independently. A sensitivity study were carried out with the spawning rate as a control parameter and two non-trivial quasi-stationary steady states of benthic biomass distributions were identified, characterised by a high and low distribution of organisms in the area, respectively. A stability diagram identifies a bifurcation point when the spawning rate is reduced by 65% and where lower spawning rates implies two different stable equilibria. The existence of multiple quasi-stationary steady states can be explained by the general circulation in the area: when spawning into the surface layer takes place from recruitment areas close to the North Sea where the out-flowing Baltic Sea surface water hinder the southward transport of pelagic larvae. The existence of multiple equilibria support the hypothesis of regime shifts in coupled physical-biological systems where modest changes in critical processes causes rapid and extensive structural changes in the ecosystem. Such changes could occur if a system is close to a bifurcation point such that small changes in critical internal biotic dynamics or in environmental conditions force the system into a new equilibria, for example due to hypoxia or changes in temperature or salinity. Finally, it is shown that model simulations of periods with hypoxic bottom water masses reduces the total benthic biomass distribution in the area significantly.