Mollusc Communities Research Articles

Benthic mollusc communities across space and through time in a hypersaline coastal lagoon, Mexico

The coast of the Yucatan Peninsula (Mexico) has undergone numerous changes over the last century as a result of population growth, shifts in land use, establishment of industries, and storm impacts. To understand how the mollusc fauna responded to these changes over time, paleoecological studies were conducted to compare historical and modern data, and to reveal information on past environmental conditions. We analyzed mollusc assemblages in sediment cores from Río Lagartos coastal lagoon, which span the last ∼70 years. Mollusc assemblages in the sediment cores were compared to a modern inventory of Mollusca fauna, which was compiled to assess species distributions associated with multiple environmental variables. Mollusc assemblages from the sediment cores (17,089 specimens), which represent 19 bivalve and 43 gastropod species, and modern inventory datasets possess the same ubiquitous species and the same feeding guilds, i.e., groups that exploit the same food resources. Nearly twice as many species were identified in the sediment cores as in the modern inventory. This finding probably reflects the fact that the mollusc community changed through time at the core sites in response to shifting environmental conditions. Nevertheless, we encountered a number of taxa in the modern survey samples, which were absent from the sediment cores. This was probably a consequence of the limited spatial coverage of the cores and small diameter of the core barrels, which precluded sampling of large taxa. We report differences in mollusc abundance and taxonomic composition in the cores across space and time, which may be related to salinity changes in the lagoon and modifications of the nearby terrestrial environment.

Měkkýši NPR Špraněk: 140 let bádání v Javoříčském krasu (střední Morava, Česká republika) [Molluscs of Špraněk NNR: 140 years of malacological research in Javoříčský karst (Central Moravia, Czech Republic)

The Špraněk NNR, as a prominent part of the Javoříčko Karst, has long been a focus of malacological research. In this study, we have assembled all the information on the mollusc fauna regarding this area by compiling literature data, records from the Natural History Museum in Prague, and data from our own field research. Since the end of the 19th century, 86 species of molluscs have been recorded. The malacofauna is dominated by preserved forest communities with a significant proportion of xerophilous and calciphilous species. The three most represented ecological groups are strictly forest (31%), woodland (15%), and euryvalent (15%) species. European and Central European species comprise the largest portion of the species composition, but a significant component is also represented by Alpine and Carpathian species, as the area lies on the border between the Bohemian Massif and the Carpathians. Despite its small area, the Špraněk NNR hosts a rich mollusc community of both conservation and zoogeographical value.

Seasonal Effects of Environmental Variables on Molluscan Communities in Çardak Lagoon (Turkish Straits)

Seasonal Effects of Environmental Variables on Molluscan Communities in Çardak Lagoon (Turkish Straits)

Drivers of the Structure of Mollusc Communities in the Natural Aquatic Habitats along the Valley of a Lowland River: Implications for Their Conservation through the Buffer Zones

The objectives of our survey were to determine the most important environmental factors within buffer zones that influenced mollusc communities and to evaluate the ecological conservation value of natural aquatic habitats (NAHs) that support mollusc species. Analysis of the spatial structure of buffer zones and catchments was based on a set of landscape metrics. Land cover classes were determined, and buffer zones within a radius of 500 m from a sampling point were marked out. Mollusc samples were collected from each NAHs. Our results showed that the number of patches and mean patch size were most associated with the distribution of mollusc species. Within patches of buffer zones, the length of the catchment boundaries with low-density housing, an increasing area of forest and pH of the water were also significant. Our results proved that landscape metrics provide essential information about catchment anthropogenic transformation. Therefore, landscape metrics and the designated buffer zones should be included in restoration plans for the river, water bodies and adjacent habitats as elements of modern, sustainable water management. NAHs located along a valley of a lowland river provide refuges for molluscs, play an essential role in the dispersal of IAS, create important protective biogeochemical barriers for rivers, constitute necessary sources of moisture and water and support microhabitats for distinct mollusc communities, especially in the context of global warming.

Diversity and seasonal variation of the molluscan community associated with the seagrass Halodule wrightii in a marine protected area in the southern Gulf of California

Diversity and seasonal variation of the molluscan community associated with the seagrass Halodule wrightii in a marine protected area in the southern Gulf of California

Community Structure of Molluscs at Batu Kijuk Village

Batu Kijuk Beach is one of the coastal areas located in West Nusa Tenggara. Its territory used for a tourist attraction and crossing to Gili Nanggu, Gili Gede and Gili Kedis. These coastal have a wealth of marine life, one of them is mollusc. This study aims to analyze the structure of mollusk community using the Systematic Plot Sampling method. This research was conducted in June-September 2019 in Batu Kijuk, Sekotong District, West Lombok, NTB. Identification and data analysis was carried out at the Marine Biology Laboratory, University of Mataram. From the results of research with 10 transects and 70 quadrants, there are 79 species with a total of 927 species of molluscs. The gastropod class consists of 65 species and 14 species of bivalves. The most common types of species found were from the family Columbellidae with 262 species, nassaridae 109 individuals, strombidae 82 species, cypraeidae 58 species and the rest were found 1-15 species. From the results of data analysis calculations, it was obtained that the highest abundance was Pyrene versicolor (3.70 Ind/m2), Nassaridae which was dominated by Hebra nigra with 2.91 (Ind/M2) and Nassarius globosus had an abundance value of 1.08 (Ind/m2). The index value of diversity (H') for molluscs in Batu Kijuk coastal is included in the high category, 2.74. The dominance index value (C) is 0.1 which means that no mollusk species dominates. The uniformity index (E) has a value of 0.62 which means moderate uniformity because only a few species dominate so that the community can be said to be quite stable.

Molluscs Across Space and Through Time in a Hypersaline Coastal Lagoon, Mexico

Biotic remains have been used in paleoecological studies to provide information on past environmental conditions. Death assemblages can be used to make inferences about past environmental conditions if modern optima and ranges of taxa are known. Gaps in knowledge about historical biotic changes often stem from a paucity of information regarding species distributions, community species richness and evenness, community structure, ecological interactions, and possible factors that caused past biotic shifts. We studied mollusc assemblages in sediment cores from Río Lagartos coastal lagoon (Mexico) and compared them to present-day mollusc communities to gain insights into environmental changes that occurred in the lagoon throughout the last century. A total of 18,779 mollusc specimens, representing 20 bivalve and 45 gastropod species, and belonging to 32 families and 48 genera, were identified in three short sediment cores collected from the coastal lagoon in 2017. Molluscs in the sediment cores were compared to an inventory of modern fauna from the lagoon, which was collected along a salinity gradient in 2017 and 2018 to link species distributions with environmental variables. Mollusc communities from the sediment cores and present-day datasets possess the same ubiquitous species and feeding guilds. Nearly twice as many species, however, were identified in the sediment cores as in the present-day inventory. We report differences in mollusc abundance and taxonomic composition in the cores across space and time, which may be related to the salinity gradient in the lagoon, temporal shift in salinity, and recent human-mediated modifications of the nearby terrestrial environment. Biotic changes driven by shifts in salinity could have been reduced salinity. Such inputs may have been driven by hurricanes, along with associated high wind velocities and geomorphologic transformations. This paleobiology study will be of use for future conservation efforts in the coastal lagoon.

Mangrove Ecosystem Services in Mitigation for Mollusca Communities in Lembar Sheet District, West Lombok Regency

Mangroves have an important role in mitigation and a significant contribution to the wealth of macrofauna. The success of mangrove management has significantly affected the diversity of macrofauna which are associated biota. The research objectives were to investigate the composition of mangroves and mollusc communities, the ecological conditions of the waters, and evidence of mangrove ecosystem services in mitigation. The research data sources are faunal, ecological, and social data. The research method uses purposive sampling and data analysis using descriptive statistics. The results showed that 7 mangrove species were found in the Cemare mangrove area. Avicennia marina, Bruguiera gymnorriza, Ceriops tagal, Rhizophora apiculata, Rhizophora mucronata, Rhizophora stylosa, and Sonnetaria alba. The dominant mangroves were Rhizopora stylosa (201 ind/Ha) and Rhizopora apiculata (146 ind/Ha). Meanwhile, the highest abundance of mollusc species was obtained by Cerithidea cingulate (38.94%) and Nerita undata (29.20%) from the gastropod class, while from the Bivalvia class, Anadara grandis (36.07%) and Anadara granosa (19.67%) were found). The condition of the aquatic environment at the research site is still within the tolerance range required for the growth and development of mollusk species. Furthermore, the majority of respondents know or are aware that mangroves have an ecological function (habitat/habitat for animals), an economic function (a livelihood location), a physical mitigation function (abrasion resistance), a non-physical mitigation function (reducing environmental heat) Good category. These results indicate that efforts need to be made to increase mangrove revegetation, given its significant benefits in mitigation.

Historical changes in mollusc communities from a temperate chenier ridge system (Mont-Saint-Michel Bay, France)

Abstract Coarse-grained chenier ridges contain abundant mollusc shells that help to reconstruct the evolution of marine ecosystems throughout the Holocene, but few temperate environments have been studied. Historical surveys of the mollusc death assemblages sampled in a chenier ridge system from the southern English Channel were compared. Present-day active ridges provide a regional-scale, time-averaged signal of the subtidal mollusc diversity. Back-barrier fossil ridges dated to the Early Medieval Period document pre-industrial baseline conditions. Shellfish farming and invasive species had little impact on mollusc death assemblages recovered from active ridges so far. However, detection of these recent changes is delayed due to taphonomic inertia as shell ages can span more than 1000 years, even in active ridges. Differences in taxonomic and functional composition between fossil and present-day ridges show a decline in grazing and carnivorous species related to macrophytobenthic habitats (seagrass beds and macroalgal belts) and a shift towards a suspensivore-dominated community. The study confirms water temperature as a major driver of ecological change in the English Channel, as warm-water species are more common in present-day ridges. Shelly chenier ridges are useful records of ecological changes in coastal environments that offer a temporal coverage far exceeding that of long-term ecosystem monitoring studies.

Observing Mollusca Benthic Diversity to Measure the Success of the Implementation of Mulung Culture as an Effort to Conserve Aquatics in the Waters of Lapang-Batang Island, Alor Regency, East Nusa Tenggara.

Mulung culture from an ecological perspective is to allows the environment to recover, traditionally. Mulung is a customary process, related to the closure of water areas for the extraction of aquatic resources. The impact of the implementation of the Mulung cultural tradition, the population of resources increases. This study aims to determine the benthic mollusk community in the Mulung area to measure the success rate of Mulung implementation. This information is needed as a starting point for sustainable fisheries development. This research uses the quadratic transect method and free collection. Then, the community structure was calculated using the diversity index, species evenness, species richness, and species density value, then continued by observing the quantitative similarity between locations calculated by the similarity index. The results showed that the species composition of benthic mollusks found in the Mulung area was 32 species, with a total of 261 individuals. The benthic mollusks that lived in the Mulung area had a Diversity Index (H’) value of 3.12 high category, Richness Index Value (R) of 5.75 is classified as high, the value of the evenness index of species (E) is 0.90, the evenness level of benthic mollusks is high and stable, the value of the dominance index (C) is 0.1, in the category no species dominates. The highest relative abundance of benthic Mollusca species overall with a value of 46.15% was owned by Ornopsis glanni species and the lowest relative abundance was Cypraea moneta, 6.90% value, the highest species density value with a value of 2.53 ind/m2, namely Ornopsis glanni and the lowest species density value is Diodora mississipppiensis, the value is 0.12 ind/m2. Meanwhile, the overall density of benthic Mollusca species obtained during the study was 17.40 ind/m2.

Molluscan Diversity Present in Tawarja River at Peth in Latur District of Maharashtra

Latur district is a part of Maharashtra's Marathwada region in the southern part, which is geographically located in the Deccan plateau between 17°52′ and 18°50′ North and 76°18′ and 79°12′ east. It is typically 631 meters (2,070 feet) above mean sea level on the Balaghat plateau. Manjara is the main river which flows on the Balaghat plateau along with its tributaries: Terna, Tawarja and Gharni. The other three tributaries of Manjara are Manyad, Teru and Lendi which flow on the northern plains. Tawarja originates near Murud in Latur taluka and joins the Manjara river at Shivani on the Latur-Ausa boundary. The study was necessary for evaluating the ecological state of water bodies with the help of freshwater molluscs with studies focusing on variety, distribution, and ecology. Two sampling sites were chosen along the Tawarja River in Peth Village for mollusk collection, and these locations were carefully organized from the river's source to its confluence point following various land use/cover patterns. Throughout the course of the research, a total of 13 taxa were noted from all sample sites. The molluscan community was represented by two classes, namely Bivalvia and Gastropoda, with three species belonging to the former and ten to the latter. Three species and one family—the Unionidae—belong to the class Bivalvia. Gastropoda class had three orders, including Mesogastropoda, three families, and seven species. The study's crucial conclusions, which demonstrated that gastropods outnumbered bivalves, were taken. These species can be utilized as bioindicators of pollution and ecosystem health. The findings of this study might contribute to better molluscan fauna management and conservation in the area.

The more Diverse Beaver Ponds are Better – a Case Study of Mollusc Communities of Steppe Streams

The more Diverse Beaver Ponds are Better – a Case Study of Mollusc Communities of Steppe Streams

Diversity of mollusc communities in some aquatic habitats of Shatsk Lake Area

Background. The paper presents the results of an original research on groups of freshwater molluscs in some water habitats of Shatsk Lake Area. The Shatsk National Nature Park belongs to the Volynian Polissia according to physical and geographical zoning. Aesthetic appeal, clear water, clean sandy lake bottoms, pine forests, etc., are attracting more visitors to the park every year. The recreational value of the Shatsk National Nature Park in the summer season is significant. The high anthropogenic load accelerates the intensity of eutrophication of lakes and promotes the overgrowth of the shores with macrophytes, which eventually leads to an increase in the density of the macrobenthos, in particular the malacofauna of the lakes. Material and Methods. Research was conducted in the summer period of 2013–2014 and 2018–2020 on some water bodies of the Shatsk National Nature Park with different trophic state including Lakes Svityaz, Pisochne, Lyutsymer, Krymne, Ostrivyanske and Somynets. Results. Freshwater molluscs are convenient subjects for water pollution stu­dies because they are good indicators of habitat quality. Svityaz and Pisochne Lakes belong to slightly mesotrophic water bodies, which are actively used for recreational purposes. Among water bodies under study, Lake Svityaz is characterized by the most significant species diversity of molluscs (23 species). Lakes Lyutsymer and Krymne are mesotrophic water bodies exposed to a high anthropogenic load. The largest number of bivalve molluscs of the genera Unio and Anodonta is characteristic of Lake Lyutsymer, while in Lake Krymne, the lowest species diversity of malacofauna (13 species) was observed. Lakes Ostrivyanske and Somynets are mesotrophic shallow water bodies. We detected a significant increase in the species composition of molluscs in these lakes during the research period. Conclusions. The research of the qualitative and quantitative composition of the malacofauna revealed an increase in the number and species diversity of molluscs. In addition, the spread of an invasive New Zealand snail Potamopyrgus antipodarum to new water bodies on the territory of Shatsk Lake Area has been recorded.

Diversity of Molluscan Assemblage in Relation to Biotic and Abiotic Variables in Brown Algal Forests.

Canopy-forming macroalgae, mainly those belonging to the order Fucales, form the so-called brown algal forests, which are among the most productive assemblages in shallow coastal zones. Their vertical, branching canopies increase nearshore primary production, provide nursery areas for juvenile fish, and sustain understory assemblages of smaller algae and both sessile and vagile fauna. The majority of benthic invertebrates inhabiting these forests have larval stages that spend some time floating freely or swimming in the plankton. Therefore, canopy-forming macroalgae play an important role as species collectors related to larval supply and hydrodynamic processes. During the past several decades, brown algal forests have significantly reduced their extension and coverage in the Mediterranean basin, due to multiple interacting natural and anthropogenic pressures, with negative consequences also for the related fauna. The aim of this research was to examine how differences in macrophyte abundance and structure, as well as environmental variables, affect the associated molluscan communities in the shallow northern Adriatic Sea. Sampling sites with well-developed vegetation cover dominated by different canopy-forming species were selected in the shallow infralittoral belt of the northern Adriatic Sea in the spring–summer period of the years 2019 and 2020. Our results confirm the importance of algal forests for molluscan assemblage, with a total of 68 taxa of molluscs found associated with macrophytes. Gastropods showed the highest richness and abundance, followed by bivalves. Mollusc richness and diversity (in terms of biotic indices) were not related with the degree of development of canopy-forming species (in terms of total cover and total volume), nor with the ecological status of benthic macroalgae at different depths. On the contrary, the variability in molluscan taxa abundances was explained by some environmental variables, such as temperature, pH, light, and nitrates concentration.

Disentangling structural and functional responses of native versus alien communities by canonical ordination analyses and variation partitioning with multiple matrices

Freshwaters are under accelerated human pressure, and mollusk communities are among its most sensitive, threatened, and valuable components. To the best of our knowledge, the overall effects of damming, environment, space, time, and invasive alien mollusk species, on structural and functional responses of native mollusk communities were not yet compared. Using historical information and recent data from a river, we aimed to investigate and disentangle these effects and evaluate the differences in structural and functional responses of natives and alien invasives to the same predictors. Variation partitioning showed that alien species were as important predictors as were environmental factors and time in explaining species composition of native freshwater mollusk communities. Aliens were more independent of environmental conditions than natives and responded to different drivers, partially explaining their invasion success. The increased abundance of some alien gastropods was positively related to taxonomic diversity, while certain alien bivalves were negatively associated with the functional diversity of native communities. We introduce a cumulative variation partitioning with multiple response (native and alien) and predictor matrices, along with a diagram to show their relations, advocating for a conceptual shift in future community ecology, from “variables to matrices” and from “multivariate analyses to multi-matrix statistical modeling”.

Predicting changes in molluscan spatial distributions in mangrove forests in response to sea level rise.

Mollusks are an important component of the mangrove ecosystem, and the vertical distributions of molluscan species in this ecosystem are primarily dictated by tidal inundation. Thus, sea level rise (SLR) may have profound effects on mangrove mollusk communities. Here, we used dynamic empirical models, based on measurements of surface elevation change, sediment accretion, and molluscan zonation patterns, to predict changes in molluscan spatial distributions in response to different sea level rise rates in the mangrove forests of Zhenzhu Bay (Guangxi, China). The change in surface elevation was 4.76–9.61 mm year−1 during the study period (2016–2020), and the magnitude of surface‐elevation change decreased exponentially as original surface elevation increased. Based on our model results, we predicted that mangrove mollusks might successfully adapt to a low rate of SLR (2.00–4.57 mm year−1) by 2100, with mollusks moving seaward and those in the lower intertidal zones expanding into newly available zones. However, as SLR rate increased (4.57–8.14 mm year−1), our models predicted that surface elevations would decrease beginning in the high intertidal zones and gradually spread to the low intertidal zones. Finally, at high rates of SLR (8.14–16.00 mm year−1), surface elevations were predicted to decrease across the elevation gradient, with mollusks moving landward and species in higher intertidal zones blocked by landward barriers. Tidal inundation and the consequent increases in interspecific competition and predation pressure were predicted to threaten the survival of many molluscan groups in higher intertidal zones, especially arboreal and infaunal mollusks at the landward edge of the mangroves, resulting in a substantial reduction in the abundance of original species on the landward edge. Thus, future efforts to conserve mangrove floral and faunal diversity should prioritize species restricted to landward mangrove areas and protect potential species habitats.

Stratigraphy and palaeoceanography of late Pleistocene molluscs from the northern coast of the Persian Gulf

We report an extraordinary discovery of marine Pleistocene strata from the north of the Persian Gulf. The Dayyer section contains a rich molluscan fauna including 26 bivalve species, Sr 87 /Sr 86 data showing that the succession is not older than 153 ka (late Pleistocene). These strata are time-equivalents of the Bakhtiari Formation, but have a very different fossil content and facies. Comparing the Dayyer molluscan community to the present-day fauna of the Persian Gulf shows that many fossil species are absent in the recent waters. The palaeoceanographic distribution of the identified bivalves shows the presence of many of them in the Plio-Pleistocene strata of the Mediterranean Basin. This may point to a temporary connection between the Persian Gulf and Mediterranean Basin during the late Pleistocene and the extinction of many bivalves in the past 153 ka

Habitat conditions of molluscs in the valleys of the Talaya and Bartat Rivers (Krasnoyarsk forest steppe, Russia) in the middle and late-Holocene

Here we have analysed the Holocene mollusc successions in the valleys of the Talaya and Bartat rivers (Krasnoyarsk forest-steppe), which, based on three radiocarbon dates, cover at least the last 6000 years. By studying more than 8700 mollusc shells, we aimed to reconstruct the development of alluvial conditions. Existing palynological data from the nearby Eleneva Cave provide deeper insights into the reconstruction of habitat conditions. A total of 13 freshwater and 18 terrestrial mollusc species were identified. Some of the land snail species are the first records for the region, with the finding of Vertigo substriata pushing its distribution limit eastward. The Talaya sequence consisted of five successional stages recognised based on Coniss analysis. The major successional pathway in the mollusc record reflects an increase in temperature and fluctuations in precipitation during the Middle Holocene. Over time, an abundant assemblage of freshwater molluscs was gradually replaced by the dominance of open-country and wetland terrestrial snails. In contrast, cooling at the beginning of the Late-Holocene resulted in a reduction in terrestrial snail species diversity at the expense of aquatic molluscs, again indicating increased moisture in riparian habitats. Although the Bartat River succession covered only the last 600 years, it showed a fairly stable mollusc community composition with some terrestrialization observed in the most recent part of the succession.

Molluscs community as a keystone group for assessing the impact of urban sprawl at intertidal ecosystems

Mollusc communities are getting endangered in the aftermath of urban sprawl because artificial structures do not surrogate natural substrates. In this study, we compared the diversity, community and trophic arrangements of molluscs among different models of artificial substrate and their adjacent natural rock, to detect relationships between some abiotic variables and the mollusc communities. Complexity, chemical composition and age were tested as potential drivers of the community. Diversity, community and trophic structure differed between natural and artificial substrates. Complexity at the scale of cm was detected as the most important factor driving the community structure. In addition, a chemical composition based on silica and/or scarce calcium carbonates seems to be relevant for molluscs, as well as for the secondary substrate where they inhabit. However, age did not seem to be a driving factor. Among the different artificial structures, macroscale complexity was detected as the main factor diverging a drastically poor community at seawall from other artificial structures. In this context, macro and microscale complexity, chemical composition and mineral type are variables to consider in future designs of artificial substrates.

Distribution of soft-bottom benthic molluscs in the Gulf of Oran (Western Algeria)

A total of 46 samples were taken in the softbottom of the Gulf of Oran, in order to study the nature of the sediments and the spatial distribution of the mollusc communities. As a result of sampling in the study area, at depth range (30 m -106 m), a total of 29 species were identified, included in two classes: Gastropoda and Bivalvia. The use of multi-variate statistical analyzes, as well as particle size analysis, made it possible to identify the main mollusc communities. Six mollusc communities were defined from faunistic and sedimentologic affinities. The malacological fauna of the Gulf of Oran is dominated by Saccella commutata (33.33%), Limatula subauriculata (20.83%) and Nucula sulcata (20.83%). The main ecological stocks are mixicole and coastal detritus species. The malacofauna of the Gulf of Oran is scarce and less diversified due to the nature of the soft bottoms (sand and gravel) and the absence of terrigenous inputs.