Invertebrate Abundance Research Articles

Effects of inundation on water quality and invertebrates in semi-arid floodplain wetlands

Floodplain wetlands play a significant role in the storage of sediment and water and support high levels of nutrient cycling that is driven by intermittent inundation. In regulated rivers, there is often a reduction in the frequency and duration of inundation and managed floodplain inundation is used as a tool to help restore wetlands. It is important to quantify the outcomes of re-introducing water to floodplain wetland systems. We examined the effects of environmental floodplain watering on water quality and three groups of invertebrates, including benthic and pelagic microinvertebrates and macroinvertebrates, in two wetlands systems on the Gwydir River system in the north of the Murray-Darling Basin. We hypothesised that a wetland inundated for longer periods of time would have altered water quality and support a greater richness and abundance of invertebrates, thus altering their assemblage structures. Water quality and the assemblage structure of all three invertebrate groups in the wetlands was significantly influenced by the time since connection (TSC) to their rivers and therefore the length of inundation. However, the response of water quality and the microinvertebrate assemblages to TSC differed between the two wetlands. Water quality was affected by an increase in six variables, including the nutrient TN and a decrease in the nutrient SRP. Microinvertebrate abundance was positively associated with TSC, but the abundance of macroinvertebrates was not. The relationships demonstrated between TSC and invertebrates indicate that the duration of inundation is important in maintaining the ecology and food webs in these and other semi-arid floodplain wetlands.

Forest–lake ecotones in a tropical forest: Terrestrial invertebrate inputs to lakes decrease with forest distance

Abstract Ecotones between tropical forests and lakes compose an ecosystem interconnection with a high abundance of terrestrial invertebrates, which represent an outstanding resource for the aquatic fauna. However, there is still little quantitative information on tropical forest contribution in terms of invertebrate inputs into lacustrine systems and the factors controlling this flux. To quantify the terrestrial invertebrate contribution into tropical lakes, we selected six lakes located in the Atlantic rainforest, south‐eastern Brazil, and used pan traps placed in the lakeshore. We focused on total abundance, biomass, and richness of insect orders. To assess the influence of forest and lake morphometry on terrestrial invertebrate inputs into lakes, we measured the forest–lake distance and considered the morphometric characteristics of each lake. Distance from forest negatively affected the invertebrate biomass reaching the lakes. The dissimilarity across different ecotones also increased with distance from the forest. Perimeter‐to‐area ratio negatively affected the invertebrate abundance, suggesting that more dendritic lakes receive more invertebrates from the forest. We estimated that annually, on average 21 tons of terrestrial invertebrates fall into the studied lakes, representing a massive food resource for the aquatic ecosystem. Hence, if the distance from the forest increases due, for instance, to severe drought or deforestation, it will create an herbaceous environment unable to provide such a quantity of insects to the water ecosystems, compromising aquatic and terrestrial trophic webs dynamics.

Occurrence and Behaviour of Shorebirds Depend on Food Availability and Distance of Beaches from Urban Settlements

Coastal ecosystems provide important feeding opportunities for shorebirds, depending on their prey availability, hydrodynamic conditions and human pressure. We aimed to evaluate short-term responses (occurrence and minimum approach distance) of shorebirds to urbanization and natural drivers on an extensive beach arc adjacent to the largest hypersaline coastal lagoon of South America. The presence of the migrant Sanderling Calidris alba and resident Collared Plover Charadrius collaris was geo-coordinated and for each record and an equivalent number of random points we measured the distance from urban settlements, swash width and invertebrate abundance (food availability) in a snapshot sampling. The distance at which each shorebird flock escaped from humans was determined (minimum approach distance). The occurrence of shorebirds was predicted by food availability, and higher crustacean density was found in areas of shorebird occurrence (37 ± 19 individuals/m2) compared to random points (10 ± 10 individuals/m2). This result highlights the importance of the beach as a feeding area and the need for conservation of shorebirds' prey. The resident Collared Plover delayed their escape from humans in areas closer to urban areas, suggesting a higher tolerance to humans on disturbed beaches, where they can prioritize the food intake rather than vigilance. The larger flocks let the researcher get closer, corroborating the risk-dilution theory stating that flocking behaviour during foraging provides protection of birds from predators. In conclusion, our results showed that monitoring of sandy beaches based on shorebirds' presence and behaviour can be a reliable tool, especially close to coastal lagoons that constitute foraging sites for these charismatic species.

Non-native Dreissena associated with increased native benthic community abundance with greater lake depth

Although the typical interaction between non-native invasive species and native species is considered to be negative, in some cases, non-native species may facilitate native species. Zebra and quagga mussels (Dreissena spp.) are aggressive invaders in freshwater systems, and they can alter energy flow by diverting nutrients from pelagic to benthic food-webs. In the last two decades, quagga mussels have largely replaced zebra mussels in shallow regions of the Laurentian Great Lakes and colonized deeper waters previously devoid of all dreissenids. Here, we aim to characterize potential positive effects of dreissenids in relation to depth on the benthic community in lakes Michigan and Huron. For this study, we used benthic survey data collected from Lake Michigan in 2015 and Lake Huron in 2017 and annual U.S. EPA Great Lakes National Program Office Long-term Biology Monitoring Program data for both lakes from 1998 to 2019. Benthic species richness and abundance (excluding dreissenids) in both lakes were almost three-fold higher in the nearshore (<70 m) compared to offshore (>70 m) communities. We found that, even though abundance of benthic invertebrates decreased with increased depth, total benthos density and biomass were higher in the presence than in the absence of quagga mussels in both lakes. Moreover, increased quagga mussel density and biomass with depth offset the lower benthos density and biomass at deeper depths, and samples with dreissenids had high densities of oligochaetes in both nearshore and offshore communities. These patterns are consistent with facilitative effects of quagga mussels on both shallow and deep-water benthic communities.

Ozone Mitigates the Adverse Effects of Diesel Exhaust Pollutants on Ground-Active Invertebrates in Wheat

There is growing evidence to demonstrate that air pollution is affecting invertebrates both directly (e.g., causing physiological stress responses) and indirectly (e.g., via changes in host plant chemistry and/or by disruption of communication by volatile odours). Many of the studies to-date have focused upon winged insects and disruption of in-flight foraging. Therefore, in this study we investigated how the community composition of predominantly ground-dwelling invertebrates in fields of winter wheat are affected by two of the most ubiquitous lower tropospheric air pollutants, diesel exhaust emissions (including nitrogen oxides–NOx) and ozone (O3), both individually and in combination, over 2 years. Pitfall traps, located within the rings of a Free-Air Diesel and Ozone Enrichment (FADOE) facility, were used to sample invertebrates. The facility consisted of eight 8 m-diameter rings, which allowed elevation of the pollutants above ambient levels (ca 49–60 ppb NOx and 35–39 ppb O3) but within levels currently defined as safe for the environment by the Environmental Protection Agency. The invertebrates collected were taxonomically identified and characterised by diet specialisation, mobility and functional group. Taxonomic richness and Shannon’s diversity index were calculated. Even under the relatively low levels of air pollution produced, there were adverse impacts on invertebrate community composition, with greater declines in the abundance and taxonomic richness of invertebrates in the diesel exhaust treatment compared with O3 treatment. In the combined treatment, pollutant levels were lower, most likely because NOx and O3 react with one another, and consequently a lesser negative effect was observed on invertebrate abundance and taxonomic richness. Specialist-feeding and winged invertebrate species appeared to be more sensitive to the impacts of the pollutants, responding more negatively to air pollution treatments than generalist feeders and wingless species, respectively. Therefore, these results suggest a more severe pollution-mediated decline in specialist- compared with generalist-feeding invertebrates, and in more mobile (winged) individuals. Understanding how invertebrate communities respond to air pollutants alone and in combination will facilitate predictions of how terrestrial environments respond to changes in anthropogenic emissions, especially as we shift away from fossil fuel dependence and therefore manipulate the interactions between these two common pollutants.

Ecosystem effects of invasive crayfish increase with crayfish density

Abstract The nature and extent of effects of increasing densities of non‐native species on stream ecosystems remain poorly understood. Non‐native crayfish are among the most invasive aquatic species and we hypothesised that, in temperate streams, the extent of trophic modification increases with non‐native crayfish density. Instream flow‐through mesocosms in the River Lune, north‐east England, were used over a 47‐day period in summer to measure density effects of invasive signal crayfish Pacifastacus leniusculus on different ecosystem components (benthic fish, macroinvertebrates, algal biomass, and leaf litter breakdown). Effects were measured through three density treatments (low, medium, and high; four, eight, or 12 crayfish with five bullhead Cottus perifretum per 1.5 m2) and two control (crayfish and fish absent; crayfish absent and benthic fish present) groups. Impacts of crayfish on macroinvertebrates (density, taxonomic composition), fish (growth, diet), algal standing stock, and decomposition rates increased with crayfish density. Direct effects of increased crayfish density were more important than indirect trophic cascade effects. Despite similar invertebrate abundance and richness across enclosures before introducing crayfish and bullhead, they differed significantly from controls at the end of the study, with &gt;80% reduction in macroinvertebrate abundance recorded in the high‐density group. Stable isotope (δ15N, δ13C) analysis showed that the trophic niche of bullhead, but not signal crayfish, changed when the species were in sympatry. Bullhead in treatment enclosures occupied a lower trophic position in the food web than those from the control group. Bullhead in the high‐density group lost 4.2% of body mass over the study period, confirming the existence of resource competition. Leaf litter break down was 59.2% faster, and algal biomass was 91.4% lower in the treatment with the highest crayfish density compared to the control without study animals. This study indicates that signal crayfish, even at a low density, can strongly alter multiple ecosystem components in streams, and emphasises the need for minimising the spread of invasive crayfish within and between streams.

Bathymetric trends in the body size, and diet of Astropecten americanus in the northwest Atlantic Ocean

Sea stars are major predators of marine invertebrates, in particular, mollusks. Data on the diet composition and the size structure of sea stars in the N.W. Atlantic Ocean are limited. Samples of sand star (Astropecten americanus) collected from three regions in the N.W. Atlantic Ocean were used to determine spatial and seasonal differences in diet and size structure. Samples were collected from ten stations during the 2009 spring and fall NMFS bottom trawl surveys. Four hundred and eighty-eight (488) prey items belonging to various taxa were identified from stomach contents of 524 sea stars of which 302 contained food. In terms of percentage contribution by number of prey items belonging to each taxon (Cn%), gastropods (40%), bivalves (22%) and crustaceans (21%) were the most important. Gastropods were more important in the diet of Southern New England (SNE) and Mid-Atlantic Bight (MAB) sea stars accounting for ∼50% of the diet in each area, and were consumed by 35–42% of the sea stars, whereas crustaceans were more important in Georges Bank (GB) where they contributed ∼83% of the diet, and were consumed by about 77% of the sea stars. There were more gastropods and foraminiferans in the stomachs of sea stars collected in fall, while crustaceans and bivalves were more common in spring samples. These differences may be due to spatial and seasonal differences in the abundance and composition of macrobenthic invertebrates. The size of sea stars decreased with depth, perhaps due to a reduction in prey abundance and higher sea star densities with depth. Additionally, length-weight relationships suggest that sea stars in GB were heavier at a given size (length) than those from SNE and MAB. This might have resulted from the latitudinal variation in the density and species composition of macrobenthic invertebrates that serve as prey for sea stars, such that densities were low on the continental shelf off Delaware-Virginia-North Carolina and relatively high in the region off southern Massachusetts and Rhode Island.

Combined per‐capita and abundance effects of an invasive species on native invertebrate diversity and a key ecosystem process

Abstract Invasive alien species (IAS) are leading to the homogenisation of taxonomic and functional biodiversity, with negative consequences for key ecosystem processes in fresh water. Invasive signal crayfish (Pacifastacus leniusculus) is expected to disrupt detritus‐based food webs by affecting leaf breakdown and/or by decreasing invertebrate density and diversity through predation. The combination of per‐capita and abundance effects of P. leniusculus in invaded ecosystems is still largely unknown. A four‐week field experiment was established in Rabaçal and Tuela Rivers (NE Portugal) to assess effects of P. leniusculus on invertebrate taxonomic and functional diversity and leaf litter breakdown following a gradient of invasion. We controlled the presence and absence of crayfish by placing the animals and leaf litter inside cages at six sites (three sites per river) according to the crayfish in situ abundance (absent, low, high). Cages were covered with coarse‐ or fine‐mesh net to allow or prevent invertebrates from accessing the leaves. Results showed that higher crayfish in situ abundance led to a decrease in abundance, richness and Shannon diversity of invertebrates and to changes in the communities’ structures. Higher crayfish abundance led also to a decrease in invertebrate functional redundancy and an increase in the percentage of invertebrate taxa with resistance forms. Leaf litter breakdown increased with crayfish presence and decreased at sites with higher crayfish abundance. Overall, signal crayfish changed the community structure of invertebrates, with potential severe long‐term effects on native communities and leaf litter breakdown. Given the widespread distribution of signal crayfish (and other crayfish species), their ecological impacts should be assessed carefully, especially in pristine freshwater ecosystems such as those described here.

Impact of Oyster (Crassostrea virginica) Reef Restoration on Benthic Invertebrates and Coastal Birds in a Subtropical Estuary

In order to mitigate the degradation of eastern oyster (Crassostrea virginica) reefs in Mosquito Lagoon (ML) along the east coast of central Florida, oyster reef restoration efforts have been in place for over 14 years. These restored reefs are successful in terms of universal oyster metrics (i.e., density, shell height, reef height) and are similar to natural reefs. However, little is known about the impact of this restoration on bird populations. ML provides a habitat for many bird species, including several listed as “threatened” by the Florida Fish and Wildlife Conservation Commission. Many of these birds rely on oyster reefs for foraging and loafing habitats. As benthic invertebrates serve as an important food source for coastal birds, we monitored the abundances and diversity of these organisms on live, restored, and dead reefs. We collected sediment samples from the reef sites pre-restoration, and one month, six months, one year, two years, and three years post-restoration. We counted benthic invertebrates present in the sediment samples, and sorted them by taxa (polychaetes, amphipods, isopods, gastropods, bivalves, decapods). Benthic invertebrate abundances on restored reefs became similar to live reefs over time (species composition, density), indicating that the prey base on restored reefs was similar to that of live reefs within 6 months. A second objective of this study was to determine if restored oyster reefs reach the same abundances, foraging behaviors, and diversity of bird species on natural, live reefs. We conducted monthly bird surveys to assess bird utilization of live, restored, and dead reefs. After three years, the abundances, behaviors, and assemblages of birds on restored reefs were similar to live reefs.

Effects of seasonal hypoxia on macroinvertebrate communities in a small reservoir

AbstractLocalized hypoxia can reduce available habitat, restrict movement and limit the abundance of aquatic invertebrates. Although cultural eutrophication, coupled with the effects of climate change, is likely to increase the frequency and extent of hypoxia in aquatic ecosystems, little is known about how oxygen gradients in small reservoirs influence spatial distribution and abundance of aquatic invertebrates. The present study evaluated the effects of environmental and biological attributes on seasonal and spatial variation of macroinvertebrates and explored how hypoxic conditions influenced littoral, benthic and pelagic macroinvertebrate communities in Lake Alvin, South Dakota. Data on reservoir conditions, in conjunction with macroinvertebrate sampling from May to October 2009–2011, were applied in an information theoretic approach to evaluate factors affecting invertebrate abundance. Hypoxic conditions were present from May to September in the lacustrine zone impacting 10%–39% of the water column. Benthic invertebrates were typically absent from the lacustrine zone during periods of severe hypoxia and were most abundant in the shallow, well‐oxygenated riverine zone. Littoral invertebrates were negatively related to the per cent of the hypoxic water column, suggesting fish, confined to shallow waters by hypoxia, may be consuming a larger portion of littoral invertebrates in their diets. Cladocera and Copepoda densities were influenced primarily by water depth and monthly precipitation. The larger size of Daphnia found in the hypoxic‐prone transitional and lacustrine zones suggested low oxygen concentrations may provide a refuge from fish predation. The results of the present study demonstrated spatial variations in near‐bottom oxygen concentrations were important predictors of macroinvertebrate and zooplankton abundance and size structure in Lake Alvin and that macroinvertebrates, particularly benthic and littoral invertebrates, could benefit from measures taken to reduce summer hypoxia.

Variability in foodscapes and fish growth across a habitat mosaic: Implications for management and ecosystem restoration

Riverine ecosystems in their natural state are complex mosaics of habitats whose conditions vary across space and time as landscape features filter prevailing hydrologic forcing. Yet, through anthropogenic alteration many large river systems have become simplified through the construction of levees and dams that reduce lateral connectivity and flow variability. The extent to which shifts in habitat mosaics create conditions that support different trophic responses that manifest in differences in fish growth across the landscape remains largely untested. This is primarily due to limitations in linking habitat features, dynamic physical processes, and trophic transfer of energy to higher taxa at the landscape scale. Here, we conducted large-scale enclosure experiments across varying habitats on a fluvial floodplain as a model system to measure factors that influence habitat-specific growth rates in multiple Chinook Salmon (Oncorhynchus tshawytscha) stocks important to fisheries and of conservation concern. Using an ecosystem approach, we reveal that landscape context, water residence time, and habitat type (agricultural, wetland, river channel) result in different hot-spots of primary and secondary food production. This variation in the aquatic foodscape resulted in significant variation in salmon growth rates and ultimate size and morphology across the landscape. Floodplain habitats generally exhibited higher water residence times as highlighted by higher specific conductance, salinity, and chlorophyll-a values. Pelagic invertebrate abundance was 10 to 100 times more abundant in the off-channel habitats compared to the river channels. The average daily growth rates of the juvenile Chinook Salmon ranged from 0.15 mm day−1 and 0.01 g day−1 in the riverine habitat to 0.55 mm day−1 and 0.07 g day−1 in the off-channel habitat. These data were used to build mixed effects models that showed the influence of chlorophyll-a concentration, water temperature and pelagic invertebrate composition on fish growth across locations throughout the experiment. As landscapes become increasingly simplified there is increased risk of losing the mosaic of habitats necessary to achieve enhanced fish growth and phenotypically diverse and sustainable salmon populations. This in-situ experimental and modeling approach can be applied to other systems to develop ecosystem indicators such as habitat-specific fish growth rates to manage landscapes and processes to support resilient fish populations.

An integrated field data and remote sensing approach for impact assessment of human activities on epifauna macrobenthos biodiversity along the western coast of Aqaba Gulf

AbstractThe Egyptian coast of Gulf of Aqaba, north of the Red Sea, suffers from severe destruction and deterioration in habitat and biodiversity due to anthropogenic activities and flooding. The present work aims to evaluate the impacts of different human activities and flooding on the biodiversity of macrobenthic invertebrates along the Egyptian coast of the Gulf of Aqaba. From January 2019 to December 2019, many field trips (12 trips) were conducted to survey macrobenthic invertebrate communities and monitor water quality at nine sites within three sectors along the study area. Each site was divided into four ecological zones and one of five categories, according to the main activities at each site. Furthermore, satellite data were used to monitor the progress of land use and turbidity in the study area. Therefore, the current study assesses the relationship between these factors and water quality and macrobenthic invertebrate distributions, similarity, diversity, dominance and abundance. The results revealed that 53 macrobenthic invertebrate species belonging to three phyla (Mollusca, Echinodermata and Annelida) and one subphylum (Crustacea) were recorded. The echinoderm Echinometra mathaei was the major eudominant species. The northern part of the Gulf was higher in abundance and diversity with low land use and lowest water turbidity, while the south part showed contrary findings. All statistical analysis confirmed that the dissolved oxygen concentration was considered the only limiting factor for the abundance and diversity of macrobenthic invertebrates. Also, the variation in activities at investigated sites affected the dominance state of species in each site. Moreover, GPS data confirmed that the tourism activity had the largest influence on marine ecosystems and biodiversity, followed by fishing and desalination practices. Otherwise, flooding has significant influence on marine habitats and creates a habitat in which other certain species can survive. In the absence of awareness, intervention and disregard for the effective coastal zone management concept, especially for the unique marine ecosystems such as the Gulf of Aqaba, the degradation of biodiversity will continue until extinction, and human life is rendered unsustainable.

Assessment of the biota condition of the Specially Protected Natural Territory “Sosnovaya Rosha” in the vicinity of a multi-lane road under construction

The article presents the results of a reconnaissance assessment of the state of biota in the area of the highway of Specially Protected Natural Territory “Sosnovaya Rosha” under construction in the city of Yoshkar-Ola (Republic of Mari El, Russia). The studied plant communities, especially mixed forests, in the forest park are characterized by a rather considerable diversity. A decrease in vitality was recorded in coniferous trees caused by low-quality drainage works. Assessment of environmental quality by IFA of the lamina of B. pendula trees has shown reasonably favorable conditions. All reservoirs are characterized by a high abundance of invertebrates. Currently, no sharp decline in the abundance of pedobionts have been noted. The diversity of dendrobiont insects with low abundance and the optimal ratio of phytophagous to predatory insects may indicate stable relationships between consorts and the determinant, a tree species. The distribution of amphibians and reptiles in the SPNT has mosaic character. We have also noted trends toward a decrease in species diversity and populations density of ornithofauna. At the moment, the road is not open for transport yet, and no sharp decline in species diversity or abundance of individuals in populations is observed.

Material type influences the abundance but not richness of colonising organisms on marine structures

Urbanisation of coastal areas and growth in the blue economy drive the proliferation of artificial structures in marine environments. These structures support distinct ecological communities compared to natural hard substrates, potentially reflecting differences in the materials from which they are constructed. We undertook a meta-analysis of 46 studies to compare the effects of different material types (natural or eco-friendly vs. artificial) on the colonising biota on built structures. Neither the abundance nor richness of colonists displayed consistent patterns of difference between artificial and natural substrates or between eco-friendly and standard concrete. Instead, there were differences in the abundance of organisms (but not richness) between artificial and natural materials, that varied according to material type and by functional group. When compared to biogenic materials and rock, polymer and metal supported significantly lower abundances of total benthic species (in studies assessing sessile and mobile species together), sessile invertebrates and corals (in studies assessing these groups individually). In contrast, non-indigenous species were significantly more abundant on wood than metal. Concrete supported greater abundances of the general community, including habitat-forming species, compared to wood. Our results suggest that the ecological requirements of the biological community, alongside economic, logistic and engineering factors should be considered in material selection for multifunctional marine structures that deliver both engineering and ecological (enhanced abundance and diversity) benefits.

Macrophyte biomass mediates trophic relationships between congeneric fishes and invertebrate communities

This study aimed to verify whether habitat complexity, assessed through macrophyte biomass, can mediate interactions between fish and invertebrate communities and help to explain the coexistence of congeneric fish species. Fish and invertebrates were sampled in ten macrophyte stands of different biomass in the Upper Paraná River floodplain. The abundance and richness of invertebrates and the diet and trophic niche breadth of Moenkhausia bonita and Moenkhausia forestii, as well as the diet overlap between these two species, were evaluated. Invertebrate abundance increased with increased macrophyte biomass but richness was not significantly affected. The diet of both fish species differed between low and high biomass stands, with the main difference being a decrease in aquatic invertebrate consumption and an increase in plant consumption with increased macrophyte biomass. In addition, the consumption of items relied on their profitability and accessibility in the environment. The trophic niche breadth of both fish species increased with increased macrophyte biomass, but there was no niche overlap. Our results indicate that even with an abundance of invertebrates, there was a decrease in the consumption of this resource, suggesting that more complex stands can be more effective refuges for aquatic invertebrates. These results highlight the role of habitat complexity in mediating interactions between fish and invertebrates and promoting their coexistence, which also helps to explain the coexistence of congeneric fish species.

Agri-environment schemes are associated with greater terrestrial invertebrate abundance and richness in upland grasslands

Agri-environment schemes are a key mechanism by which agricultural sustainability is encouraged by subsidising farmers to adopt environmentally friendly management (e.g. reduction of inputs) to maintain and enhance the delivery of biodiversity-associated ecosystem services. Studies testing the efficacy of agri-environment schemes have yielded varying results, and few have focused on upland (marginal or Less Favoured Area) grassland (> 150 m above sea level) where productivity is poor. This study used a factorial field experiment to examine patterns in plant communities and terrestrial invertebrates between agri-environment scheme and conventionally managed semi-improved and improved upland grasslands, using 90 spatially paired fields. Total plant species richness and rare plant species richness (those with < 10% occurrence) were unaffected by agri-environment scheme management, but were significantly higher on semi-improved than improved grasslands. Total and rare invertebrate abundance and family-level richness were unrelated to grassland type (semi-improved or improved). Total and rare invertebrate abundances were 4% and 218% higher, and total and rare invertebrate family-level richness were 17% and 14% higher in agri-environment scheme than conventionally managed fields, respectively. Here, we show that agri-environment scheme management of marginal or Less Favoured Area upland grassland was associated with higher multi-taxa invertebrate abundance and richness associated with swards indicative of wetter conditions with lower dominance of perennial ryegrass (Lolium perenne) and greater coverage of other native grass species compared to conventional management. This suggests that agri-environment schemes may maintain, enhance or offset declines in terrestrial invertebrates and their associated ecosystem service delivery by maintaining more diverse swards, and suggests that they make a positive contribution to biodiversity conservation.

Correlation between Coral Reef Condition and the Diversity and Abundance of Fishes and Sea Urchins on an East African Coral Reef

Coral reefs are one of the most diverse marine ecosystems, providing numerous ecosystem services. This present study investigated the relationship between coral reef condition and the diversity and abundance of fishes, on a heavily fished East African coral reef at Gazi Bay, Kenya. Underwater visual censuses were conducted on thirty 50 × 5 m belt transects to assess the abundance and diversity of fishes. In parallel, a 25-m length of each of the same transects was recorded with photo-quadrats to assess coral community structure and benthic characteristics. For statistical analyses, multi-model inference based on the Akaike Information Criterion was used to evaluate the support for potential predictor variables of coral reef and fish diversity. We found that coral genus richness was negatively correlated with the abundance of macroalgae, whereas coral cover was positively correlated with both the abundance of herbivorous invertebrates (sea urchins) and with fish family richness. Similarly, fish family richness appeared mainly correlated with coral cover and invertebrate abundance, although no correlates of fish abundance could be identified. Coral and fish diversity were very low, but it appears that, contrary to some locations on the same coast, sea urchin abundance was not high enough to be having a negative influence on coral and fish assemblages. Due to increasing threats to coral reefs, it is important to understand the relationship among the components of the coral reef ecosystem on overfished reefs such as that at Gazi Bay.

Explorando o impacto da presença de detritos exóticos na comunidade de invertebrados aquáticos e no processo de decomposição foliar em um riacho na Mata Atlântica

Abstract: Aim In this study, we examined the effects of non-native leaf litter on the functioning of an Atlantic Forest stream ecosystem. Methods Were tested two predictions: (i) Leaf litter from the native trees with high nutritional quality will have higher decomposer’s activity and faster litter decomposition; (ii) Given the presence of anti-grazing defenses, we also hypothesized that non-native leaf litter would be colonized by fewer invertebrates and that native species would be more species-rich. For this, in a forest stream (Florianópolis, SC, Brazil) we conduct the experiment to understand the decomposition and biological colonization of leaf litter among two non-native (Eucalyptus sp. and Pinus radiata D. Don) and two native trees (Ficus eximia Schott and Alchornea triplinervia (Spreng) Mull. Arg). Results Our predictions were partially corroborated. The percentage of dry mass remaining was lower for the native leaf litter. The invertebrate abundance and richness, and functional feeding groups vary between native and non-native leaf litter. Invertebrate abundance was higher in non-native Eucalyptus detritus, largely due to the high larval abundance of Chironomidae (Diptera). Conclusions Our results indicate that the presence of non-native riparian species can modify leaf decomposition and aquatic invertebrate communities in subtropical streams, with potential consequences for ecosystem functioning.

The Impact of Lantana camara on Invertebrates and Plant Species of the Groenkloof Nature Reserve, South Africa.

Invasive plant species have negative ecological impacts such as displacing indigenous plants and invertebrates. These invasive plant species affect biodiversity by impacting indigenous vegetation and the food webs associated with this vegetation. We assessed how Lantana camara affects indigenous plant species richness and invertebrates and their feeding guilds in riparian habitats inside the Groenkloof Nature Reserve in South Africa. We showed: (1) A lower abundance and morphospecies richness of invertebrates as well as lower numbers of plant species in lantana-invaded habitat as compared to indigenous bush and grass-dominated habitats. (2) A Negative association between plant species richness and L. camara above ground mass and shoot density, but no association was found between plant species richness and the size of L. camara invaded areas. This finding suggests a link between the reduction in overall invertebrate abundance and morphospecies richness and the replacement of native plant species by invasive lantana. (3). This increased biomass in natural vegetation was even more evident for detrivores as compared to other feeding guilds. Extensive invasion by L. camara is affecting the quality of riparian ecosystems especially for invertebrates that rely on decaying plants and animals as food and this will affect overall biodiversity.

Epibiont community composition of red mangroves Rhizophora mangle are contingent on root characteristics

Foundation species traits that structure communities are rarely experimentally examined; thus, a predictive understanding of their functions lags behind patterns of observed species associations. Red mangrove Rhizophora mangle roots form complex living habitats that support diverse epibiont communities, making them a model system for testing links between variation in foundation species traits and associated biodiversity. Here, we compared epibiont community composition between living and non-living mangrove roots, as well as root mimics, to test how foundation species traits affect community structure. We also quantified the community structure of associated mobile invertebrates to examine their relationship with secondary foundation species (e.g. sponges, bivalves) that grow on the roots. After 14 mo of colonization and succession, substrate composition (i.e. mangrove, wood, PVC) had significant effects on community composition, richness, and abundance of sessile epibionts and mobile invertebrates. Non-living mangrove roots were 5 times more likely to deteriorate, and consequently had the lowest epibiont richness and abundance. We found strong positive relationships between mobile invertebrate richness and the abundance, measured as biomass, and richness of sponges and bivalves, suggesting that variation among roots in secondary foundation species play an important role in mediating mobile invertebrate community composition. This study highlights the functional role of habitat structure and how rapidly that function can be lost without biogenic maintenance. Our results indicate the importance of facilitation cascades in fostering diverse mobile invertebrate communities and highlight both advantages and limitations in using artificial structures in restoration programs.