Ocean Acidification and Mollusc Settlement in Posidonia oceanica Meadows: Does the Seagrass Buffer Lower pH Effects at CO2 Vents?

Ocean acidification has been broadly recognised to have effects on the structure and functioning of marine benthic communities. The selection of tolerant or vulnerable species can also occur during settlement phases, especially for calcifying organisms which are more vulnerable to low pH–high pCO2 conditions. Here, we use three natural CO2 vents (Castello Aragonese north and south sides, and Vullatura, Ischia, Italy) to assess the effect of a decrease of seawater pH on the settlement of Mollusca in Posidonia oceanica meadows, and to test the possible buffering effect provided by the seagrass. Artificial collectors were installed and collected after 33 days, during April–May 2019, in three different microhabitats within the meadow (canopy, bottom/rhizome level, and dead matte without plant cover), following a pH decreasing gradient from an extremely low pH zone (pH < 7.4), to ambient pH conditions (pH = 8.10). A total of 4659 specimens of Mollusca, belonging to 57 different taxa, were collected. The number of taxa was lower in low and extremely low pH conditions. Reduced mollusc assemblages were reported at the acidified stations, where few taxa accounted for a high number of individuals. Multivariate analyses revealed significant differences in mollusc assemblages among pH conditions, microhabitat, and the interaction of these two factors. Acanthocardia echinata, Alvania lineata, Alvania sp. juv, Eatonina fulgida, Hiatella arctica, Mytilys galloprovincialis, Musculus subpictus, Phorcus sp. juv, and Rissoa variabilis were the species mostly found in low and extremely low pH stations, and were all relatively robust to acidified conditions. Samples placed on the dead matte under acidified conditions at the Vullatura vent showed lower diversity and abundances if compared to canopy and bottom/rhizome samples, suggesting a possible buffering role of the Posidonia on mollusc settlement. Our study provides new evidence of shifts in marine benthic communities due to ocean acidification and evidence of how P. oceanica meadows could mitigate its effects on associated biota in light of future climate change.

The Orava dam reservoir – an important site of aquatic molluscs in north-western Slovakia

Mollusc assemblages of the Orava reservoir, the biggest dam reservoir in Slovakia, were studied in 2020. The reservoir, built in 1941–1953, is situated in north-western Slovakia. Sixteen aquatic mollusc species (13 gastropods, 3 bivalves) were recorded. Valvata piscinalis (O. F. Müller), Radix auricularia (Linnaeus) and Gyraulus parvus (Say) were the most frequent; they were recorded in more than ten sites each. Rich mollusc assemblages, composed mainly of gastropods, were found in sites with rich littoral vegetation of macrophytes. The bivalve diversity and abundance were very small, especially compared to the other studied dam reservoirs. The current results were compared with the previous surveys. The occurrence of Radix lagotis (Schrank) is its first reliable record in Slovakia. Viviparus acerosus (Bourguignat), Aplexa hypnorum (Linnaeus), Anodonta cygnea (Linnaeus), non-native Potamopyrgus antipodarum (Gray) and Physa acuta (Draparnaud) were recorded in this area for the first time and their sites are outside their known range in Slovakia.

Drilling predation on Antarctic tusk shells: first records on Recent scaphopods from the Southern Hemisphere

Drillholes on shells are one of the few predation marks preserved in fossil molluscs, providing an opportunity to study and quantify predator-prey interactions in the palaeontological record. Among these, reports of drilling predation on scaphopods are rare, and such information from Antarctica is non-existent. We describe the finding of drillholes on scaphopods recovered from Recent mollusc assemblages between depths of 246.5 and 454.0 m in West Antarctica. The predation traces located in the middle sectors of two preyed shells belonging to Siphonodentalium dalli and Dentalium majorinum are identified as Oichnus and are interpreted as produced by naticids, probably Pseudamauropsis aureolutea. These new records constitute the first reports of drilling predation on scaphopods in Antarctica and also for Recent scaphopods of the Southern Hemisphere.

Freshwater molluscs of the Zrmanja and Krupa Rivers (Croatia) – the role of these rivers as a refuge of threatened and endemic species

The Balkan region is inhabited by hundreds of endemic species of freshwater molluscs but the information on their distribution, as well as that on the distribution of more common and widespread species, is still insufficient; most areas have no complete inventories of their mollusc faunas. The Zrmanja is one of the largest rivers in the Adriatic part of Croatia. Its freshwater molluscs were studied in the last decade, resulting in a substantial body of distributional data. The main objective of this study was to summarise and analyse the recent distributional information on its freshwater molluscs, with special reference to endemic or threatened species. In total 33 freshwater mollusc species were found in the Zrmanja River and its tributaries at 73 sites. The middle section of the Zrmanja River and its largest tributary, the Krupa River, were the richest studied parts. Dalmatinella fluviatilis Radoman, Tanousia zrmanjae (Brusina) and Islamia zermanica Radoman, endemic to the Zrmanja catchment area, were found in the middle and lower sections of the river. Their occurrence is scattered and limited in area; T. zrmanjae is probably on the verge of extinction. The occurrence of the endemic Belgrandiella kusceri (Wagner), Hadziella sketi Bole and Kerkia sp. in springs or underground waters and an abundant population of Unio elongatulus C. Pfeiffer in the Zrmanja and Krupa Rivers is also noteworthy. The area can be regarded as an important part of the Balkan region, one of world’s hotspots of global biodiversity. Although it is protected, there are still anthropogenic factors that are negatively affecting or may affect the mollusc assemblages.

PONTO-CASPIAN AND MEDITERRANEAN FAUNAL AND FLORAL RECORDS OF UPPER PLEISTOCENE-HOLOCENE SEDIMENTS FROM THE İZMİT GULF (MARMARA SEA, TURKEY)

İzmit Gulf is located between Kocaeli and Armutlu peninsulas at east of Marmara Sea and the interaction area of North Anatolian Fault Zone (NAFZ) and Marmara Graben systems. In this study, the faunal and floral contents (ostracod, foraminifer, mollusc and diatom) of the samples belonging to seven drilling cores were studied and obtained the radiocarbon and optically stimulated luminescence (OSL) age data in order to establish on the Black Sea – Marmara Sea - Mediterranean water connections and palaeoenvironmental changes. The sediments in this study are Late Pleistocene-Holocene aged and only cover the Marine Isotope Stages MIS-5 (interglacial), MIS-3 (an interstadial period between MIS-4 and MIS-2 glacial epochs) and MIS-1. The determination of ostracod and mollusc fauna of the Mediterranean and Ponto-Caspian origin provide important clues to water exchange between the Mediterranean and the Black Sea. Although some Mediterranean originated ostracods occur sporadically with low abundance, absence of foraminiferal fauna and existence of Ponto-Caspian ostracods together with fresh water and cosmopolitan diatom flora indicate that the area strongly interacted with the Black Sea waters during MIS-5. The faunal and floral characteristics of the sediments deposited during MIS-3, clearly denote that the Izmit Gulf was connected with the Black Sea and the Mediterranean Sea at the beginning of MIS-3 (ca. 52.0 - 40.0 ky BP) and the shallow shelf areas were frequently affected by both the Black Sea discharge and Mediterranean input. A thick Holocene sedimentary sequence recovered from the southern Hersek Burnu drilling cores reflects the environmental changes after the latest Black-Mediterranean seas connection. The studied ostracod and mollusc assemblages are mainly characterized by the Mediterranean originated species with a few relict Ponto-Caspian fauna. Also, the benthic foraminiferal assemblages are dominated by normal marine and euryhaline species, reflecting the salinity fluctuations in the Holocene interval.

THE SANGIRAN FOSSIL SHELL ASSEMBLAGES CATALOGUE

Abstrak. Katalog Himpunan Fosil Kerang Sangiran. Makalah ini merupakan pemutakhiran himpunan fosil cangkang Sangiran di Jawa Tengah. Tujuannya untuk mendokumentasikan dan menyajikan gastropoda dan kerang dari seri Kalibeng atas dan Pucangan Bawah Kubah Sangiran dari periode Plio-Pleistosen. Tercatat 61 taksa moluska hingga tingkat genus. Informasi yang dikumpulkan dari kumpulan moluska ditentukan oleh sejarah geologi dan lingkungan Sangiran. Mereka diasosiasikan dengan fasies yang berbeda: a) napal masif dan lempung biru, b) lapisan batugamping lempung, c) lempung kelabu berlumpur, d) breksi vulkanik dan lahar dan e) lempung hitam, dan terdiri dari sedimen yang merepresentasikan lingkungan laut hingga rawa yang mengarah ke perkembangan kontinental. Pola kuantitatif yang dicatat dalam kumpulan moluska menjelaskan palaeo-lingkungan dan hubungan antara kumpulan palaeodataset yang mapan dari analisis dan tingkat variabilitas dalam data paleontologi. Selain itu, cangkang yang teridentifikasi dapat digunakan sebagai referensi untuk perwakilan taksonomi Sangiran dan moluska di lapisan Kalibeng dan Pucangan Cekungan Solo di Jawa Tengah. Abstract. This paper is an update of fossil shell assemblages of Sangiran in Central Java. It is aimed to document and present the gastropods and bivalves from the Upper Kalibeng and Lower Pucangan series of the Sangiran dome from the Plio-Pleistocene period. There are 61 mollusc taxa recorded up to the genus level. Information gathered from mollusc assemblages are determined by the geological and environmental history of the Sangiran. They are associated with different facies: a) massive marls and blue clays, b) layered clayey limestone, c) silty gray clay, d) volcanic breccia and lahars and e) black clays, and composed of sediments representing marine to swampy environments leading to continental development. The quantitative patterns recorded in mollusc assemblages elucidate the palaeoenvironment and the relationship between the established palaeodatasets of analysis and the levels of variability in palaeontological data. Moreover, the identified shells may be utilized as a reference for Sangiran and molluscan taxonomic representative in Kalibeng and Pucangan layers of Solo Basin in Central Java.

Human- and climate-induced changes of mollusc assemblages of millpond deposits in the valley of Jarosławianka Stream (Poland)

Deposits from a millpond in the Jarosławianka Stream valley (Sławno Plain, NW. Poland) were subject to malacological analysis in order to reconstruct the history of environmental transformations of the pond from its establishment in 1351 to the end of its functioning in 1960. Thirty five mollusc taxa occurred in the pond during its functioning: 21 taxa of water snails, 11 bivalves, and 3 terrestrial snails. Six phases of development of the pond were distinguished, based on the mollusc assemblages: phase I (1351–1450 CE) – very favourable habitat conditions, high species richness and diversity; phase II (1450–1490 CE) – deterioration of habitat conditions – decrease in the number of species and individuals; phase III (1490–1590 CE) – improving conditions and reappearance of species which had occurred in the pond in phase I; phase IV (1590–1750 CE) – the least favourable conditions and poor malacofauna in terms of species number and abundance; phase V (1750–1790 CE) – renewed development of the malacofauna; phase VI (after 1790 CE) – end of functioning of the pond. The phases of pond development were associated with hydrological transformations, resulting from climatic factors and human economic activity.

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.