Mollusc Communities Research Articles

Diet of snow crab in the Barents Sea and macrozoobenthic communities in its area of distribution

Abstract This article investigates the diet of the snow crab (Chionoecetes opilio) and its feeding intensity in the Barents Sea. Data show that snow crab has a diverse diet that includes almost all types of benthic invertebrates living in the Barents Sea. There are differences between the diets of females and males and of juveniles and adults. Juveniles and females typically occupy shallow areas with communities of bivalve molluscs, while males typically live deeper on slopes and depressions where polychaetes and crustaceans are the most abundant groups. Stomach contents were analysed to determine the species composition and frequency of occurrence of various benthic taxa. Consumption of food was estimated and compared with data from the Russian seas of the Pacific region. The total annual consumption of macrozoobenthos by snow crab was calculated in accordance with its current distribution in the Barents Sea. Snow crab consumes at least 30 000 tonnes of benthos annually, which amounts to 0.1–0.2% of the total macrozoobenthic biomass in the investigated area. The population of snow crab causes the largest impact on the benthic communities in the northeastern part of the Barents Sea and near the south side of the Novaya Zemlya archipelago.

Biological Conservation of Molluscs Based on Spatial and Temporal Distribution in Tropical Tidal Lake, Medan-Indonesia

The tidal lake ecosystem is formed by the flow of the Belmera River and seawater through a tidal process along a course of 12 km from Belawan (Malacca Strait). This lake has a tidal lake that has the characteristics of fresh water to brackish water and Mollusc communities from freshwater species to brackish water species. This study was performed to develop a mollusc conservation strategy based on the spatial and temporal distribution of Mollusca in the tides. The study was conducted from September 2018-August 2019. Mollusc samples were taken every month at high tide and low tide using a Petersen grab tool. Nine Mollusca species, consisting of three bivalves and six gastropods, were identified. Polymedosa expansa is a mollusc species that is considered for conservation. The population size of P. expansa is small, and its distribution is limited to the northern lake. P. expansa was found only in September at high tide and in December at low tide. Competition among Mollusca and habitat availability are obstacles to the survival of P. expansa. The habitat of P. expansa is mangrove, and therefore a conservation approach was carried out through improvement of mangrove quality.

Biological responses to extreme weather events are detectable but difficult to formally attribute to anthropogenic climate change

As the frequency and intensity of extreme events such as droughts, heatwaves and floods have increased over recent decades, more extreme biological responses are being reported, and there is widespread interest in attributing such responses to anthropogenic climate change. However, the formal detection and attribution of biological responses to climate change is associated with many challenges. We illustrate these challenges with data from the Elbe River floodplain, Germany. Using community turnover and stability indices, we show that responses in plant, carabid and mollusc communities are detectable following extreme events. Community composition and species dominance changed following the extreme flood and summer heatwave of 2002/2003 (all taxa); the 2006 flood and heatwave (molluscs); and after the recurring floods and heatwave of 2010 and the 2013 flood (plants). Nevertheless, our ability to attribute these responses to anthropogenic climate change is limited by high natural variability in climate and biological data; lack of long-term data and replication, and the effects of multiple events. Without better understanding of the mechanisms behind change and the interactions, feedbacks and potentially lagged responses, multiple-driver attribution is unlikely. We discuss whether formal detection and/or attribution is necessary and suggest ways in which understanding of biological responses to extreme events could progress.

Algal complexity positively affects the abundance, richness and diversity of molluscan assemblages of a semiarid hypersaline mangrove

Marine macroalgae serve as habitats that provide ideal shelter for a rich and diverse community of associated molluscs, but the true effects of the complexity of these habitats on fauna are still poorly understood. Replicates of four macroalgal species: Gracilaria domingensis (Kutzing) Sonder ex Dickie 1874, Solieria filiformis (Kutzing) Gabrielson 1985, Gracilaria cuneata Sonder ex Kutzing 1859 and Dictyota ciliolata Areschoug 1854 of a hypersaline estuary were collected to investigate the effects that macroalgal habitat complexity index has on the abundance, richness and diversity of associated molluscs. Habitat complexity index was determined by measuring several morphological attributes of each replicate of the four macroalgae species as well as weight and the fractal dimension. The studied macroalgae differed in habitat complexity index, with Gracilaria domingensis being the most complex. Microgastropods were the most species rich and abundant group of molluscs with 59 of 90 species and 876 of the total 1006 individuals. Mollusc community abundance and diversity differed significantly among the studied species of macroalgae. Habitat complexity had a positive effect on associated mollusc abundance, richness and diversity. This study revealed a rich biodiversity of micromolluscs associated with the studied macroalgae and reinforces the positive effects that increased habitat complexity has on the coexistence of this rich and diverse fauna in phytal ecosystems. Conservation efforts to protect hypersaline mangroves should include the protection of macroalgae banks as an important tool for habitat management and the maintenance of the associated biota.

Abundant and rare species may invoke different assembly processes in response to climate extremes: Implications for biodiversity conservation

Climate change is expected to increase the magnitude and frequency of extreme climate events. Accurate predictions of the effects of these events on communities and designing scientific recovery and management programs for biodiversity require an understanding of the mechanisms underlying differentially-abundant taxa responses. Here, we assessed an arboreal mangrove mollusk community before and after an extreme cold event (ECE) to determine the effects of the ECE on deterministic and stochastic processes, as well as succession, in abundant and rare taxa. We found that the ECE caused increasingly divergent succession of mollusks, as reflected by changes in species richness and species turnover; these changes more strongly affected the abundant taxa than the rare taxa. The relative importance of stochastic and deterministic processes in shaping mollusk communities was also altered after the ECE, although the effects differed between the abundant and rare species assemblages. That is, in response to the ECE, the abundant assemblage maintained a consistent level of mutualism while significantly increasing divergent succession by reducing ecological drift, decreasing niche breadths, weakening interspecific competition, promoting environmental selection, and increasing dispersal limitations. In contrast, the rare assemblage maintained high levels of divergent succession by increasing ecological drift, improving environmental filtering, decreasing niche breadths, weakening both interspecific competition and mutualism, and eroding spatial limits. Thus, species richness, species turnover, abundant species, and rare taxa should be the recommended indicators for the ECE; deterministic and stochastic processes should be mechanistic indexes for community coping with the ECE and also be theoretical indicators for biodiversity conservation and restoration after the ECE. More broadly, our results highlight that mechanistic indexes (deterministic and stochastic processes) and community structure indicators (species richness and species turnover) should be considered in differently-abundant taxa (abundant and rare taxa) in order to more accurately predict the effects of climate change on communities and devise targeted management and conservation strategies for the world's biodiversity.

Functional diversity of reef molluscs along a tropical-to-temperate gradient

Global warming is leading to range shifts of marine species, threatening the structure and functioning of ecological communities and human populations that rely on them. The largest changes are seen in biogeographic transition zones, such as subtropical reef communities, where species range shifts are already causing substantial community reorganisation. This causes functional changes in communities over subtropical latitudes, though a baseline functional understanding remains elusive for many taxa. One key marine taxon are molluscs, which provide many ecosystem services, are important prey for fishes and are also fisheries targets themselves, but remain largely unstudied. Here, we examine the trait composition, functional diversity, and functional redundancy of mollusc assemblages along the tropical-to-temperate transition in Japan (25° to 35° Northern latitude). Specifically, we use a trait database of 88 mollusc species from 31 subtropical reefs along the Pacific coast of Japan to show that trait composition of mollusc assemblages changes continuously along the latitudinal gradient. We discover that functional diversity of mollusc assemblages decreases with increasing latitude, a pattern associated with declines in functional dispersion. Moreover, we find a clear distinction between tropical and subtropical mollusc assemblages, with substrate-attached, suspension feeding bivalves more abundant in the tropics and free-living gastropod grazers more prevalent at higher latitudes. Our trait-based evidence in this study shows a contraction and almost complete shift in the functioning of marine mollusc assemblages at biogeographic transition zones and our trait database facilitates further study. Our findings provide evidence of the changing taxonomic and functional composition of extant mollusc communities with latitude, pointing to potential pertinent changes and tropicalisation of these communities with rapid ocean warming.

The effects of metaldehyde on non-target aquatic macroinvertebrates: Integrating field and laboratory-based evidence

The use of pesticides has historically helped improve agricultural productivity, although their continued use may have unforeseen effects upon the natural environment when not applied appropriately. Metaldehyde is a commercial pesticide widely used to reduce crop losses resulting from terrestrial mollusc damage. However, following precipitation and runoff it frequently enters waterbodies with largely unknown consequences for aquatic fauna. This study represents one of the first attempts to examine its potential effects on aquatic macroinvertebrate communities at sites known to have experienced elevated metaldehyde concentrations alongside unaffected control sites. In addition, a series of laboratory exposures specifically examined the effects of metaldehyde on the survivorship of non-target aquatic mollusc species. When the entire aquatic macroinvertebrate community and aquatic mollusc community were considered, limited differences were observed between metaldehyde affected and control sites based on field data. Laboratory exposures highlighted that for the molluscs examined, gastropods (Bithynia tentaculata, Planorbis planorbis, Radix balthica and Potamopyrgus antipodarum) had a greater tolerance to metaldehyde than bivalves (Sphaerium corneum and Corbicula fluminea). However, the concentrations required to reduce survivorship of all species were much greater than those ever recorded historically under field conditions. The results suggest that the differences in the community composition recorded between sites exposed to elevated metaldehyde concentrations and control sites were probably due to nutrient loading (N and P from agricultural fertilizers) rather than metaldehyde. However, these results do not negate wider concerns regarding metaldehyde use, particularly issues caused when ingested by vertebrate wildlife, livestock or children and pets in domestic settings.

Gene expression differences between abalone that are susceptible and resilient to a simulated heat wave event

Sudden increases in water temperature can lead to mortality of cultured and wild mollusc communities during the summer months. The frequency and severity of mortality events are expected to increase as climate changes. The molecular basis for individual survival ability is poorly understood. To better understand signatures and mechanisms affecting survival we analyzed the gene expression profiles of greenlip abalone (Haliotis laevigata) classified as susceptible or resilient to laboratory induced heat stress both prior to, and at three time points throughout, the heat stress event. We detected 487 genes that were significantly differentially expressed between resilient and susceptible abalone (28 of these were significantly differentially expressed over all three time points and 26 were significantly differentially expressed throughout two of the three heat stress trial sampling points). These 54 genes also demonstrated a similar relative expression level difference between resilient and susceptible abalone in samples collected six months prior to the heat stress event. Three distinct co-expression networks incorporating these genes were also identified. The most informative transcriptomic differences between resilient and susceptible abalone throughout the heat stress trial were associated with metabolism (e.g. Mitofusin 1) and immune process (e.g. Multiple epidermal growth factor-like domain 10, Lysozyme). These functional mechanisms may enable resilient individuals to endure heat wave events. These signatures could be used to predict an individual's resilience. The findings have application in aiding stock selection for the aquaculture industry, to provide greater resilience to global climate change.

Can relict-rich communities be of an anthropogenic origin? Palaeoecological insight into conservation strategy for endangered Carpathian travertine fens

Western-Carpathian travertine fens developed on deep-circulation groundwater are highly localised and harbour unique communities that combine rare species of calcareous fens and salt marshes, with many species considered glacial or Early-Holocene relicts. Using a multi-proxy palaeoecological approach, we tested the assumption of naturalness and Holocene continuity of the current plant and mollusc communities occupying one of the best-preserved travertine fens in Europe. Our novel results, based on two complete cores throughout the fen deposits, document an anthropogenic origin of the current communities, despite their richness in rare and relict species. The habitat originated in the very beginning of the Holocene, later it was encroached by a semi-open woodland with spruce and alder and then by a dense reed bed that suppressed fen species even more than woodland encroachment. When compared with a fen site on shallow-circulation groundwater, the Holocene succession to woodlands has been blocked by travertine formation, allowing survival of light-demanding relicts in small patches. The current communities were established once the woody plants, and especially reed, were reduced by medieval land use. The community itself is therefore not relict, but it harbours probable descendants of relict populations that survived in neighbouring small refugia throughout the Holocene. Our results strongly support the need for active conservation actions as mowing and extensive grazing, mimicking the traditional type of land use, which has conditioned the recent travertine assemblages in the past.

Materials on the fauna of bivalve mollusks (Mollusca, Bivalvia) of the Taz river basin (Western Siberia)

Based on a study of samples made by the author, 70 species of freshwater bivalves belonging to 6 genera and 2 families are recorded for the Taz River basin (north of Western Siberia). An annotated list of bivalves of the Taz basin is provided, with data on species’ range, their findings in Western Siberia and within the studied area. Some information about bionomics and abundance of bivalves are given. 45 species are for the first time registered in this basin. Most studied molluscan communities are characterized by low species richness; the distribution of species by their occurrence was extremely uneven. 22 species are characterized as rare. The highest species richness of bivalves was found in river channels, rivers and brooks; the lowest - in temporary habitats. The core of the fauna is constituted by species with broadest range (cosmopolitan, trans Holarctic, trans Palearctic) as well as by taxa with European Siberian type of distribution. From the taxonomic point of view, the bivalve fauna of the Taz basin is relatively separated from the faunas of other river basins of Western Siberia and is more similar to the fauna of the Lower Yenisean zoogeographic province (sensu Starobogatov [1986]).

Resilience of marine invertebrate communities during the early Cenozoic hyperthermals

The hyperthermal events of the Cenozoic, including the Paleocene-Eocene Thermal Maximum, provide an opportunity to investigate the potential effects of climate warming on marine ecosystems. Here, we examine the shallow benthic marine communities preserved in the late Cretaceous to Eocene strata on the Gulf Coastal Plain (United States). In stark contrast to the ecological shifts following the end-Cretaceous mass extinction, our data show that the early Cenozoic hyperthermals did not have a long-term impact on the generic diversity nor composition of the Gulf Coastal Plain molluscan communities. We propose that these communities were resilient to climate change because molluscs are better adapted to high temperatures than other taxa, as demonstrated by their physiology and evolutionary history. In terms of resilience, these communities differ from other shallow-water carbonate ecosystems, such as reef communities, which record significant changes during the early Cenozoic hyperthermals. These data highlight the strikingly different responses of community types, i.e., the almost imperceptible response of molluscs versus the marked turnover of foraminifera and reef faunas. The impact on molluscan communities may have been low because detrimental conditions did not devastate the entire Gulf Coastal Plain, allowing molluscs to rapidly recolonise vacated areas once harsh environmental conditions ameliorated.

Influence of macroalgal morphology on the functional structure of molluscan community from hypersaline estuary

Studies based on functional approach seek to understand the ecological roles developed by species as well as their interactions with the environment in which they are inserted. The hypothesis tested was that functional richness and diversity of molluscan community will be higher at the most complex macroalgal habitat. The study was carried out at Casqueira river estuary (Rio Grande do Norte, Brazil). Three species of macroalgae were collected—Gracilaria domingensis (Kutzing) Sonder ex Dickie 1874, Gracilaria cuneata Areschoug 1854, and Solieria filiformis (Kutzing) P.W.Gabrielson 1985—and the composition of seven functional traits of the mollusk fauna associated to the algae was characterized in 22 categories. The highest values of functional richness and diversity were for macroalgae with greater habitat complexity (G. domingensis). Some functional traits were influenced more by macroalgal morphology, like ‘life way,’ feeding strategy, body size, and larval development. Thus, we show that the greatest richness and functional diversity of the communities is related to sites with more complex habitat, sites with more shelter and refuge, and food. This highlights the importance of the quality of habitat for shellfish communities and shows that it can be assessed from the use of a functional approach.

Mollusc Communities at Maros and Pangkep Karst Caves, South Sulawesi

Mollusc Communities at Maros and Pangkep Karst Caves, South Sulawesi

Diversity assessment and protection strategies for the mollusk community in the southern Dongting Lake

Diversity assessment and protection strategies for the mollusk community in the southern Dongting Lake

Structure and dynamic of mollusk communities of small oxbow lakes and the determing factors (the Khoper river valley, Penza oblast)

Structure and dynamic of mollusk communities of small oxbow lakes and the determing factors (the Khoper river valley, Penza oblast)

STRUKTUR KOMUNITAS MOLUSKA DI PADANG LAMUN PERAIRAN PULAU BELITUNG PROVINSI BANGKA BELITUNG

Pulau Belitung memiliki banyak pulau-pulau kecil dengan tutupan lamun yang cukup bervariasi, tempat berbagai jenis moluska hidup, namun keanekaragaman moluska di perairan ini belum banyak diketahui. Penelitian di Pulau Kelayang (stasiun BLTS01), Pulau Kepayang (stasiun BLTS02), Pulau Mendanau (stasiun BLTS03), Pulau Sekutai (BLTS04), Pulau Sebongkok (stasiun BLTS05), Pulau Ruk (stasiun BLTS06) dan Pulau Kalimambang (stasiun BLTS07), telah dilakukan pada tanggal 29 Agustus hingga 9 September 2018. Tujuan dari penelitian ini, untuk mengetahui struktur komunitas dan kepadatan moluska. Metode penelitian yang digunakan adalah metode transek kuadran, yang dilakukan dari tepi pantai tegak lurus ke arah tubir. Dari hasil penelitian ini ditemukan sebanyak 22 jenis moluska yang terdiri dari 10 jenis dari kelas bivalvia dan 12 jenis dari kelas gastropoda. Anadara antiquata, Pinna bicolor dan Gafrarium pectinatum dari kelas bivalvia; Lambis lambis dan Strombus urceus dari kelas gastropoda memiliki penyebaran yang luas. Kepadatan moluska tertinggi terdapat di stasiun BLTS06 (23,283 individu/ha) dan terendah di stasiun BLTS03 (283 individu/ha). Isognomon isognomum merupakan jenis yang mendominasi stasiun BLTS06. Nilai indeks keanekaragaman jenis (H’) berkisar antara 2,42-3,52 dan masuk dalam kategori keanekaragaman sedang. Indeks kemerataan jenis (J’) berkisar antara 0,71-0,86. Hasil penelitian ini menunjukkan bahwa komunitas moluska di perairan ini masih berada dalam kondisi cukup baik.

Response of the mollusc communities to environmental factors along an anthropogenic salinity gradient

Anthropogenic salinisation of freshwater ecosystems is frequent across the world. The scale of this phenomenon remains unrecognised, and therefore, monitoring and management of such ecosystems is very important. We conducted a study on the mollusc communities in inland anthropogenic ponds covering a large gradient of salinity located in an area of underground coal mining activity. A total of 14 gastropod and 6 bivalve species were noted. No molluscs were found in waters with total dissolved solids (TDS) higher than 17.1 g L−1. The share of alien species in the communities was very high in waters with elevated salinity and significantly lower in the freshwaters. Canonical correspondence analysis (CCA) showed that TDS, pH, alkalinity, nitrate nitrogen, ammonium nitrogen, iron, the content of organic matter in sediments, the type of substrate and the content of sand and gravel in sediments were the variables that were significantly associated with the distribution of molluscs. The regression analysis revealed that total mollusc density was positively related to alkalinity and negatively related to nitrate nitrogen. The taxa richness was negatively related to TDS, which is consistent with previous studies which indicated that a high salinity level is a significant threat to freshwater malacofauna, causing a loss of biodiversity and contributing to the colonisation and establishment of alien species in aquatic ecosystems.

Age and depositional environment of the Xiaheyan insect fauna, embedded in marine black shales (Early Pennsylvanian, China)

The Early Pennsylvanian Xiaheyan entomofauna (Ningxia, China) is among the earliest assemblages of winged insects known so far, and therefore provides an essential input on deciphering the early diversification of this group. Despite its evolutionary significance, both the age and depositional environment remained poorly constrained. Here, we present high-resolution documentation of litho- and biofacies, biostratigraphy and geochronology of the up to 100 m thick type section. Accordingly, the insect-bearing strata are of latest Bashkirian (latest Duckmantian) to middle Moscovian (Bolsovian) age. The sediments, lithostratigraphically assigned to the Yanghugou Fm., represent a regressional marine sequence formed at the southern margin of the Qilian Inland Sea. Intercalations of crevasse channels and splays that laterally interlock with marine black shales and bioclastic limestones point to deposition in an interdelta bay. Ground-touching waves provoked the erosion of muds at shallow depths leading to mass mortalities among mollusc communities due to rising anoxia, turbidity and water turbulence. In addition, bottom currents transported mud intraclasts towards the basin, where sinking insects that reached the bay via winds and surface currents were buried sub-contemporaneously with bivalves below the storm wave base. Observed differences in insect preservation and assemblage composition across the sequence are found to correlate with lithology and are best explained by distance from land, and the action of events inducing insect carcasses to sink, such as storms. The proposed taphonomic model represents a new fossilization pathway from land to sea and provides new directions for prospecting Paleozoic deposits in the search for insects.

Seasonal variation of mollusc's community living in a tropical lagoon (Aby lagoon, Côte d'Ivoire)

Seasonal variation of mollusc's community living in a tropical lagoon (Aby lagoon, Côte d'Ivoire)

PENGARUH FAKTOR LINGKUNGAN TERHADAP POLA PENYEBARAN MOLUSKA PADA EKOSISTEM MANGROVE ALAMI DAN HASIL REHABILITASI

Mangrove ecosystem is a habitat of Molluscs (Gastropoda and Bivalvia). This ecosystem is always influenced by environmental factors. This study aims to determine the influence of environmental factors on the distribution patterns Molluscs of natural mangrove ecosystems in Pannikiang Island, Barru Regency and rehabilitation mangrove ecosystem in Tongke-tongke village, Sinjai regency. This research uses the quantitative method. Environmental factors measured were temperature and salinity of the water, aswell as carbon and nitrogen content of sediment. Samples of Molluscs (Gastropoda andBivalves) and sediments were taken randomly. The observations of the Molluscan community include the composition of Mollusc species (Gastropoda and Bivalvia) anddispersal patterns. Data were analyzed by using multiple linear regression. The results showed that the distribution pattern of Molluscs (Gastropoda and Bivalvia) at both sites was not significantly different and the temperature, salinity, carbon, and nitrogen sediments also did not affect the Mollusk distribution pattern in both sites.