Shallow Littoral Zone Research Articles

Counting fish at night using artificial light: transect survey of common bream Abramis brama and northern pike Esox lucius abundance as an example.

Visual transect counting of large-bodied fish using artificial light at night in a shallow littoral zone (<1 m water depth) is introduced as a complementary survey method for fishes such as common bream Abramis brama and northern pike Esox lucius that are under-represented in standard gillnet surveys. The results suggest that transect counting at night and applying necessary corrections for environmental variables could provide a simple and repeatable method to assess the presence and abundance of large-bodied fishes in lakes with satisfactory water clarity.

Non-marine ostracods from the Cretaceous Banyaweol and Geoncheonri formations (Gyeongsang Basin, Korea) in the collections of the Geological Museum, KIGAM: Taxonomy, biostratigraphy, palaeobiogeography and palaeoenvironment

ABSTRACT The Geological Museum of the Korea Institute of Geoscience and Mineral Resources (KIGAM) houses a large collection of microfossils. From these collections, 14 species belonging to six genera of non-marine ostracods from the Banyaweol and Geoncheonri formations of the Gyeongsang Basin, South Korea are identified: Cypridea sp. 1, C. sp. 2, C. sp. 3, C. sp. 4, C. sp. 5, C? sp. 6, Lycopterocypris triangularis, L. cf. profunda, Candona declivis, C. sp. Cypria cf. elata, Djungarica sp. Ziziphocypris costata and Z. rugosa. The biostratigraphic correlation based on L. triangularis and C. declivis from the Cenomanian Banyaweol Formation suggests that these species appeared at a much earlier stage than the previous records from China. Ostracods of the Banyaweol Formation may represent a transitional fauna during the mid-Cretaceous faunal turnover in East Asia. However, L. cf. profunda and C. cf. elata suggest a Turonian – Santonian age (probably extend upwards into Campanian) for the Geoncheonri Formation. Many non-endemic species of both formations indicate that these faunas were linked with ostracod faunas of East Asia, providing evidence of active faunal exchanges and migration. The palaeoenvironments of both formations are interpreted as ephemeral waterbodies and unstable shallow-littoral zone of lakes based on faunal compositions.

Deepwater Renewal in a Large, Deep Lake (Lake Geneva): Identifying and Quantifying Winter Cooling Processes Using Heat Budget Decomposition

AbstractWintertime deepwater renewal, which is important for heat–oxygen–nutrient exchange in lakes, is traditionally considered to be mainly driven by 1D vertical convective cooling. However, differential cooling between shallow and deep waters can produce density currents that flow into deep layers. In order to determine the role that these two cooling processes play in deepwater renewal, field measurements and 3D numerical modeling were combined to investigate heat content dynamics in Lake Geneva's large basin, the Grand Lac (maximum depth 309 m), during an exceptionally cold air spell in early 2012 where complete overturning had been reported. In a novel approach, the heat budget of the lake was decomposed, which allowed the identification and quantification of the heat budget components. The heat budget decomposition revealed that vertical convective cooling only penetrated to 200 m and that lateral advection was not only caused by density currents being discharged from the shallow littoral zone of the Grand Lac, but also from the Lake's shallow Petit Lac basin (maximum depth 75 m); the latter was found to be the main driver of heat content decrease in the deep layers of the Grand Lac below ∼200‐m depth. These findings provide unique insight into heat exchange processes that cannot be obtained from field data or numerical simulations alone. Heat budget decomposition proved to be a powerful, universally applicable tool for quantifying the contribution of alternative deepwater renewal processes. This is important, since deepwater renewal by convective cooling is weakening due to persistent global warming.

Habitat suitability of Unionidae host fish in the Rhine Delta

Unionid populations are declining worldwide as they are threatened by anthropogenic habitat alterations, the introduction of invasive alien species and the effects of climate change. Several studies have focused on the habitat preferences of adult mussels but none to date have reported on the importance of the habitat preferences of host fish species. The aim of this study was to determine the habitat preferences of unionid host fish species in the Netherlands, to examine potential differences between native and alien host fish species, and to evaluate the effect of alien host fish species on unionid dispersal. Species sensitivity distributions (SSDs) were constructed for the range of occurrences and laboratory tolerance of host fish species in the Netherlands for water temperature, substrate type, flow velocity, and water depth. A case study was selected to assess the suitability to substrate type, flow velocity and water depth of a novel river habitat along longitudinal training dams in the river Waal. Unionid host fish species in the Netherlands preferred shallow littoral zones (0.1 m) with low flow velocity (0.05 m/s), an average water temperature of the Rhine delta (15°C), and most substrate types (ranging from silt to cobbles). Boulder substrate was the most limiting factor of the abiotic factors assessed for both native and alien host fish species. Management options for unionid populations should include host fish species in their assessments while focusing on creating and maintaining areas with limited boulders and implementing alien host fish species removal measures.

Taphonomic signatures on the pearl oyster Pinctada from Arabian Gulf, Saudi Arabia

A total of 886 valves of the pearl oyster Pinctada were collected from 12 sites in Al-Uqair beach along the Saudi Arabian Gulf coast in January 2021 in order to document their taphonomic signatures. Thirteen ichnospecies of 5 ichnogenera were identified and illustrated. These traces were produced by clionid sponges (Entobia cretacea, E. ovula, E. geometrica, E. laquea, E. cateniformis, Entobia isp.), durophagous drillers (Oichnus paraboloides, O. ovalis, O. simplex, and Oichnus isp.), traces of vermetid gastropods (Renichnus isp.) polychaete annelids (Caulostrepsis isp.) and barnacle attachment scars (Anellusichnus circularis). The Pinctada shells act as hard substrate for colonization by serpulid worm, Spirorbis sp., bryozoans, barnacles, and other bivalves. Ichnogenus Oichnus was the most abundant (53.73%), followed by Entobia (44.58%), Anellusichnus (0.51%), Caulostrepsis (0.34%), and Renichnus(0.84%). The thin-shelled and smooth skeletons of Pinctada were preferable for the abundant durophagous drillers (Oichnus traces) and clionid sponges (Entobia traces) during the lifetime of the pinctadas, in contrast to endolithic bivalves (Gastrochaenolites borings) which need thicker seashells for the settlement. Occurrence of different encrusters and bioeroders on the internal surfaces of many pinctadas confirmed the postmortem origin of the signatures. Disarticulation, fragmentation, and abrasion among the collected pinctadas might be attributed to their mode of life as epifaunal byssate, filter-feeder bivalves in the shallow littoral and sublittoral zones of the continental shelf under strong currents conditions.

Aerogenic route of metals entering lake Ladoga

Studies have shown that the entry of metals and other pollutants by aerogenic means into Lake Ladoga is associated with the presence of both remote and local sources of entry into the atmosphere. In this regard, Lake Ladoga is in a vulnerable state, as studies have shown – since often the metal content in precipitation is higher than in water. This is especially dangerous for the shallow littoral zone of the lake, where the dilution rate is low due to the volume of water. This showed their presence in water, sediments and fish, and most importantly – the impact on the biota and, above all, on the ichthyofauna, since fish are able to accumulate pathological information during their life cycle. Toxicosis has become a mass phenomenon in these waters, which has affected the natural reproduction of fish with a prolonged effect on populations and ichthyocinosis in general. The inflow of metals and other pollutants of organic nature (xenobiotics) in the form of dry and wet precipitation forms a polluting surface runoff, which is associated with difficulties in carrying out preventive measures.

Environmental determinants of coarse woody habitat in gravel pit lakes

Matern S, Robichon C, Nikolaus R, Monk CT, Arlinghaus R. 2023. Environmental determinants of coarse woody habitat in gravel pit lakes. Lake Reserv Manage. 39:259–272. Coarse woody habitat (CWH) is an important structural habitat in freshwater ecosystems. In natural lakes, CWH accumulates over centuries alongside the succession of littoral tree communities. Newly created gravel pit lakes have difficulties in accumulating CWH due to their young age. Additionally, CWH presence might be negatively affected by shoreline development, where wood is removed to facilitate recreational activities such as angling. We studied 26 gravel pit lakes with an age ≤ 55 yrs in Lower Saxony, Germany, to quantify CWH density and to understand the impact of environmental factors, including lake morphology, lake age, wind direction, abundance of riparian trees, and the presence or absence of fisheries management, on CWH density. We sampled small and large CWH in the littoral zone of the study lakes using a transect-based approach. Density of CWH was lower in German gravel pit lakes than in North American natural lakes. In gravel pit lakes, we detected increasing densities of small CWH with increasing numbers of large trees on the shore and with increasing littoral slopes in lakes managed for recreational fisheries. Large CWH density was positively affected by lake age, by the density of large trees on the shore and with wind from land, and again by steep littoral slopes in lakes managed for recreational fisheries. We recommend that recreational fisheries managers and individual anglers maintain CWH in shallow littoral zones to promote fish habitats in generally low-structured gravel pit lakes.

The current ecological and ichthyotoxicological state of the Svir bay of Lake Ladoga

A significant part of the water area of the bay is represented by a shallow littoral, which is characterized by the highest biodiversity and bioproductivity. Approximately 90% of benthic organisms known for Lake Ladoga are inhabitants of the littoral zone. The littoral and water areas gravitating towards it are a spawning and feeding place for all fish species living in the lake. The Svir Bay of Lake Ladoga is located in the southeastern part of the lake water area. Its area is 260 km2. The present study in the water area of the Svirskaya Bay with an assessment of the state of the ichthyofauna was carried out in the summer of 2022, and the previous one - in the eighties of the last century The article presents the materials of biological and chemical-analytical studies in the Svir bay of Lake Ladoga, which is of great fishery importance. The ecological and ichthyotoxicological state of the studied water area and the most important importance of the ichthyofauna in assessing the state of its individual sites are shown. Thus, the shallow littoral zone turned out to be more polluted compared to the more remote from the coast and more deepened southern part of the lake. A higher level of pollution of the littoral, which occupies a significant part of its water area, negatively affected the ichthyofauna of the reservoir and its reproduction, which led to an impact on fish stocks, especially valuable species, and the structure of the ichthyocenosis of the lake as a whole. The results of the research also showed that the condition of the lip as a whole has improved somewhat compared to the eighties of the last century, when the last ichthyotoxicological studies were conducted in this water area. Taking into account the state of the ichthyofauna and other indicators of the study, the pollution level of the Svir Bay of Lake Ladoga can be characterized as weakly expressed sublethal.

How influential is the role of oligotrophication on the integrity of fish assemblages in the littoral zone?

Food web theory predicts that one of the consequences of oligotrophication is the decline in fisheries following the establishment of nutrient-deficient conditions and low biogenic production. However, emerging evidence suggests that more complex trophic interactions, induced by plankton composition, dietary diversification, temporal and spatial heterogeneity, variations in fish age and size structure can lead to ecosystem responses that deviate from theoretical predictions; especially in the shallow littoral zone. In this study, two end-to-end modelling strategies are used to characterize potential food web structural shifts and overall ecosystem productivity in response to oligotrophication. Our modelling strategy draws upon empirical and theoretical evidence from the Bay of Quinte, a semi-enclosed embayment in northeastern Lake Ontario that has been subjected to phosphorus (P) abatement strategies in the 1970s. We first show that the role of food abundance has been a primary factor shaping fish production, but the fish community gradually responded to the reduced availability of pelagic staples of their diet by displaying greater reliance upon alternative sources, including benthic and other autochthonous (or even allochthonous) food items. Our analysis further suggests that degree of diet overlap between competing trophic guilds can significantly modulate realized biomass levels. The composition of the autotrophic community is another major confounding factor that can induce significant variations from the predicted food web productivity patterns in response to oligotrophication. Overall, our analysis suggests that the proposed reduction of the ambient total phosphorus levels may not necessarily trigger a significant decline in fish biomass in the Bay of Quinte.

Impacts of anthropogenic pressures on underwater light conditions and diatom functional group distributions in mountain lakes

Underwater light availability and exposure of ultraviolet radiation (UV) in mountain lakes is mainly controlled by dissolved organic matter and ice cover. However, both of these factors are affected by climate warming and other anthropogenic pressures. Still, little is known of the impacts of long-term fluctuations in underwater light conditions onto functional distribution of diatoms, species sensitive to changes in climate and UV penetration in mountain lakes. Two mountain lakes in the Italian Alps were analysed using paleolimnological approaches to investigate impacts of anthropogenic pressures (e.g., climate warming, acidification) on underwater light availability, exposure to UV and diatom functional group distributions, focusing on the post-industrial era. Contemporary diatom communities were collected from the main habitats in the shallow, high irradiance littoral zones of these lakes and geochemical proxies describing the development of lake-water transparency and carbon dynamics were analyzed from the sediment cores covering the time period from ca. 1400 CE to present. The geochemical data indicate that cultural acidification decreased lake-water organic carbon concentrations in both lakes, which suggests increased light availability and UV exposure during the past century. The responses of the studied lakes to anthropogenic pressures varied, as the lake situated at a lower altitude with a larger catchment showed only a few biotic changes indicating higher resilience, whereas the lake situated at higher altitude showed distinct changes in its ecological status. In this alpine lake, almost 30% of the diatom functional groups shifted from benthic to planktic during the post-industrial era. The role of increased light availability and UV exposure as a driver of diatom functional group distributions could not be unambiguously separated, and such diatom assemblage changes have been shown in many regions and most closely linked to a warming climate. However, low guild functional groups, prevalent also in the contemporary samples from the shallow littoral zone, dominated the diatom communities throughout the studied period, suggesting high tolerance to UV radiation.

Ecosystem-based management outperforms species-focused stocking for enhancing fish populations.

Ecosystem-based management is costly. Therefore, without rigorously showing that it can outperform traditional species-focused alternatives, its broad-scale adoption in conservation is unlikely. We present a large-scale replicated and controlled set of whole-lake experiments in fish conservation (20 lakes monitored over 6 years with more than 150,000 fish sampled) to examine the outcomes of ecosystem-based habitat enhancement (coarse woody habitat addition and shallow littoral zone creation) versus a widespread, species-focused alternative that has long dominated fisheries management practice (i.e., fish stocking). Adding coarse woody habitats alone did not, on average, enhance fish abundance, but creating shallow water habitat consistently did, especially for juvenile fish. Species-focused fish stocking completely failed. We provide strong evidence questioning the performance of species-focused conservation actions in aquatic ecosystems and instead recommend ecosystem-based management of key habitats.

Nonmarine ostracod fauna from the Lower Cretaceous Shinekhudag Formation (southwest Mongolia): taxonomy, biostratigraphy, and paleoecology

AbstractThis work provides the detailed investigation (taxonomy, biostratigraphy, and paleoecology) of a nonmarine ostracod fauna from the Shinekhudag Formation in Gobi–Altai area, southwest Mongolia. The samples from two sections (Tsagaan Tsuvarga and Oshih Hollow East) yielded various ostracods assigned to nine species belonging to six genera: Cypridea verrucata Neustrueva, 1974, C. ihsienensis Hou, 1958, C. unicostata Galeeva, 1955, C. tumefacta Neustrueva, 1974, Yumenia cf. Y. oriformis Hou, 1958, Scabriculocypris subscalara Zhang and Chen in Ye et al., 2003, ?Trapezoidella sp., Candona sp., and Vlakomia ulanense Neustrueva, 1977. The biostratigraphic application of our taxonomic results suggests that the age of the Shinekhudag Formation is Barremian–Aptian. In addition, the ostracod fauna shows strong affinities to faunas from northeast China and potentially northwest China, providing evidence of faunal exchanges between these regions and southwest Mongolia. The new discovery of Vlakomia ulanense indicates that mid-Cretaceous (Albian) species in northeast China probably originated in Mongolia at the time of deposition of the Shinekhudag Formation. Two ostracod assemblages in the studied sections reflect that different paleoenvironment settings have existed during deposition; the Tsagaan Tsuvarga Section represents a shallow-littoral zone of athalassic (inland) saline lake under arid climate, and the dominance of cypridoideans of the Oshih Hollow East Section is indicative of ephemeral water bodies.

Structural and Physical Factors As Predictors of the Species Distribution And Diversity of Dragonflies and Damselflies (Odonata) in an Upland Storage Reservoir

The negative impact of storage reservoirs on the environment has been well documented, but it appears that under certain circumstances these reservoirs can also help to protect biodiversity. The distribution of adult dragonflies and damselflies was studied in relation to eight environmental variables, in an upland storage reservoir and its feeder rivers located in South-East Poland (East-Central Europe). A total of 25 species were recorded, including 22 in the reservoir. Submerged and floating plants, width of the shallow littoral zone and the water movement/current were found to be the key drivers of the species distribution (pCCA, NMDS). Five species (Ischnura elegans, Sympetrum sanguineum, Platycnemis pennipes, Calopteryx splendens and Erythromma viridulum) were responsible for over 70% of the dissimilarities between the riverine and reservoir sites (SIMPER). In addition, Ischnura elegans, Orthetrum albistylum and Calopteryx virgo were distinguished as the indicator species (IndVal analysis) for the upland river-reservoir hydrological system. Our results highlight some design features of reservoirs that may help to maintain the diversity of odonates, as well as many other groups of aquatic organisms, as the former are well-known indicators of general biodiversity.

Fish distribution and behaviour with regard to the time of day and the anthropogenic structural modification of the shallow littoral.

The shallow littoral zone is under a variety of environmental drivers and anthropogenic pressures. As these factors are highly dynamic, they may affect the distribution and behaviour of littoral fish. The present study investigates the effect of the time of day and the benthic habitat type on the shallow littoral fish community. Diel variations in total fish abundance, community composition, species abundance and behaviour were studied in two neighbouring stations in the Patraikos Gulf (Greece): one with cobble seabed cover and another with anthropogenic habitat structural modifications, like large artificial blocks, rocks and other objects. Visual census revealed that community composition differed depending on both the time of day and the habitat type. Total abundance was highest in the morning, whereas both diel abundance and habitat use were found to be taxon specific, with most species showing a preference for the artificial rocky habitat. Diel differences in species behavioural patterns were also observed, with a greater percentage of fish being active during the day (morning and noon) rather than in the afternoon. Although the fish community does not change entirely within a day or between adjacent locations, it is significantly variable in even small spatial and temporal scales. Consequently, there are implications for the design and implementation of sampling designs and monitoring plans that should be consistent in time of day throughout the sampling period and include locations structurally modified by humans. Furthermore, the management of the shallow littoral zone should consider the small-scale variability and alternate anthropogenic habitat with natural unaltered patches.

Convective circulation influences horizontal movement by planktonic crustaceans in the littoral zone of a mesotrophic lake

Abstract Crustacean zooplankton perform diel vertical and horizontal migrations in lakes to avoid predators and/or exploit food resources more efficiently. Crustaceans may also move passively with convective flows that are generated by the nocturnal cooling of the surface water. Water in the shallow littoral zone cools faster than deeper pelagic waters. Therefore, bottom water moves from inshore to the pelagic zone while surface water moves in the opposite direction. The purpose of this study was to determine if crustaceans performed horizontal movements in the bottom and surface layers of a mesotrophic lake, Lake Obsterno in north‐west Belarus. We installed plankton nets horizontally in the bottom and surface layers of the lake at three sites located at different distances from the shore. We hypothesised that (1) if crustaceans performed diel horizontal migration, they would move in identical directions in the bottom and surface layers either from nearshore to open waters in the evening and back in the morning, or vice versa; (2) if crustaceans moved with convective flows, they would be carried to the shore in the surface layer and to the open waters in the bottom layers. Day and night air temperatures differed by more than 10°C over 24 hr. We assumed that the rates of convective currents were similar to those reported for other lakes exposed to a similar range of air temperatures. Rates of convective currents were also measured in Lake Obsterno and varied between 0.6–0.7 cm/s. These rates of convective currents were shown to exceed the cruise speed of planktonic crustaceans. The direction of movement of the most abundant taxa coincided with the direction of convective currents in more than 90% of the cases in the bottom layer and 70–80% of the cases in the surface layer. The abundance of invertebrate predators (mainly predatory cladocerans and boatmen (Hemiptera, Heteroptera) was negatively related to the abundance of crustaceans in the surface layer. Deviations in the distribution patterns of some crustacean species compared to distributions induced by convection currents in the upper layers may have been associated with the avoidance of invertebrate predators and/or predator grazing. Abundances of crustaceans were positively correlated between the sites located at different distances from the shore, and individual taxa were positively related to each other indicating that they moved in the same direction. Based on the fact that the directions of crustacean movements and convective currents mostly coincided, we concluded that convective currents passively carried the crustaceans. At low light intensities and low predation pressure (by visual fish predators), the direction of horizontal movement by zooplankton was mainly determined by convective circulation generated by cooling of the lake surface. Actively swimming planktonic invertebrate predators are likely to move in the same direction as herbivorous crustaceans. Therefore, predators could influence zooplankton distribution regulated by convective flows. We suggest that studies of horizontal migration and coupling between pelagic and littoral zones need to account for diurnal water currents in lakes.

Depth-distribution of lake benthic diatom assemblages in relation to light availability and substrate: implications for paleolimnological studies

We analyzed the depth distributions of benthic diatoms in two adjacent, but hydrologically distinct subalpine lakes (Lakes Soiernseen, S-Germany). Lake Unterer Soiernsee is affected by marked water-level fluctuations and is light-penetrated to the bottom most of the year, while Lake Oberer Soiernsee provides more stable conditions and an extended aphotic zone. Mixed samples of epiphytic, epilithic, epipsammic and epipelic periphyton were taken in one-meter depth steps by scuba divers. Most of the common benthic diatoms occurred in distinct depth-areas. RDA analyses showed that depth was strongly correlated with species distribution in both lakes. Depth-constrained cluster analyses indicated three distinct diatom community zones in each lake. A shallow littoral zone hosting mainly epiphytic and epilithic species and a deeper littoral zone with mainly epipsammic and epipelic taxa existed in both lakes. Additionally, a highly disturbed near-shore littoral zone with diatoms adapted to unstable conditions (aerophilic taxa, pioneer species) was found in Lake Unterer Soiernsee, and a deep-water pelagic zone with mainly planktonic taxa in Lake Oberer Soiernsee. Light availability, substrate, physical stressors and nutrient concentrations were linked closely with water depth. While light availability affected the ratio of benthic and planktonic diatoms, substrate type influenced benthic diatom assemblage structures. Diatoms occurring in surficial sediments of the aphotic zone represent an ideal cross-section of the recent diatom assemblage of the lake, including benthic and planktonic species. However, sediment samples taken in light-flooded depths are inappropriate for studies based on shifts between benthic and planktonic taxa, because in situ benthic species dominate the surface-sediment assemblages, while settled tychoplanktonic and planktonic species occur less frequently. A diatom-inferred depth model was created for each lake to prove the usability for down-core studies using weighted-averaging approaches. For both lakes these models are highly appropriate to reconstruct past fluctuations in water-transparency or lake-level. With regard to the development of diatom-based TP-transfer-functions for Bavarian mountain lakes, we found it is highly important to consider lake depth and transparency. Based on the findings of this study we recommend the creation of two different training-sets, one for deep or low-transparency lakes with an aphotic zone including both benthic and planktonic diatoms, and another one for shallow, clear water lakes solely using benthic diatoms.

Positive interspecific associations consistent with social information use shape juvenile fish assemblages.

Social information obtained from heterospecifics can enhance individual fitness by reducing environmental uncertainty, making it an important driver of mixed-species grouping behavior. Heterospecific groups are well documented among fishes, yet are notably more prevalent among juveniles than more advanced life stages, implying that the adaptive value of joining other species is greater during this developmental period. We propose this phenomenon can be explained by the heightened ecological relevance of heterospecifically produced cues pertaining to predation risk and or resources, as body-size uniformity inherent in early ontogeny yields greater overlap in predator and prey guild membership across juveniles of disparate taxa. To evaluate the putative role of information in shaping juvenile fish assemblages, we employed a joint species distribution model (JSDM), identifying nonrandom relationships among fishes collected in 785 seine hauls within the shallow littoral zones of a subtropical island. After accounting for species-environment relationships, which explained 39% of observed covariation in the abundance of 11 taxa, we detected high rates of positive association (84% of significant correlations) predominantly between mutual foraging guild members, consistent with assemblage patterns predicted to evolve under widespread interspecific information use. Affiliations occurred primarily between species characterized by neutral (i.e., noninteracting) or negative (i.e., predator-prey) relationships in later life stages, supporting the notion that heightened niche overlap due to body size homogeneity acted to increase the pertinence of information among juveniles. Taxa exerted varying degrees of influence on assemblage structure; however Eucinostomus spp., a gregarious generalist with exceptional information-production potential, had an effect several times that of all other species combined, further evidencing the likely role of information in motivating observed relationships. Co-occurrence and qualitative behavioral data inferred from remote underwater video surveys reinforced these conclusions. Collectively, these results suggest that positive interactions linked to information exchange can be among the principal factors organizing juvenile fish assemblages at local scales, highlighting the role of ontogeny in mediating the relevance and exploitation of information across species.

Dynamics and Relationship between Plankton Organisms in the Littoral Zone of a Large Plain Reservoir at the Beginning of the Vegetation Season

The dynamics and relationship between planktonic algae, bacteria, protozoa, invertebrates, and viruses were studied at different sites in shallow littoral zones of the Rybinsk Reservoir (Upper Volga) in April–June. The features of seasonal succession of different components of the littoral plankton community have been identified. The spring peak in the development of phytoplankton, caused by diatoms and cryptophyte algae, is weakly pronounced in shallow littoral waters. An increase in the number of bacteria and development of protozoa and zooplankton in the littoral occurs earlier than in the open part of the reservoir. Consequently, the clear-water phase starts earlier and has a shorter duration. An important role in the nutrition of the littoral zooplankton, in addition to phytoplankton, is played by heterotrophic protozoa and bacteria developing through the use of both auto- and allochthonous organic substances.

Rhodolith beds along the southeastern Mediterranean inner shelf: Implications for past depositional environments

Abstract The inner structure of multitaxonomic boxwork rhodoliths from a seabed located off of the Northern Israeli coast was explored as a tool to understand past depositional environments of the shallow littoral zone. Studied rhodoliths consist of superimposed, successive growth stages formed by different encrusting biota. The types of growth stages include fruticose encrusting coralline algae layers, and layers of serpulid tubes, grainstone or encrusting coralline algae. Carbon dating of radial sections cut from along the growth axis of two large rhodoliths (~8 cm radial sections) suggests that the transition between these layers occurred at the same time, and that layers dominated by different phyla have significantly different growth rates, ≥0.3 ~0.8 mm yr−1 for the serpulid layers and 0.1–0.4 mm yr−1 for the coralline algae stages. Layers of sediment grains between some of the growth stages suggest that the successions occurred during high turbidity periods in the surrounding water, possibly induced by heavy rain or storm events. Radio-carbon dating of the largest rhodolith samples shows a record of such environmental influence in the area dating back 366 ± 57 years cal. B.P. Studies on boxwork rhodolith growth stages are a potential archive of past depositional environments in the shallow littoral zone.

Revision of Hyalopale (Chrysopetalidae; Phyllodocida; Annelida): an amphi-Atlantic Hyalopale bispinosa species complex and five new species from reefs of the Caribbean Sea and Indo-Pacific Oceans.

The formerly monotypic taxon, Hyalopale bispinosa Perkins 1985 (Chrysopetalinae), is comprised of a cryptic species complex from predominantly tropical embayments and island reefs of the Western Atlantic and Indo-Pacific Oceans. Hyalopale species are of meiofaunal size (length: 1-2.8mm), but considered non-interstitial, with the majority of species inhabiting a singular habitat of shallow littoral zones among algae and epifauna overlying sediments in rubble. Hyalopale adults exhibit notochaetal fans characterized by the presence of lateral and midline notochaetal spines. Species of Hyalopale can be distinguished by the shape of glass-like notochaetal paleae and the number of densely stacked ribs. Hyalopale bispinosa forms a western and eastern Atlantic species complex, comprising the type species, Hyalopale bispinosa s.s., a comparatively larger form with the highest number of notochaetal paleael ribs from Florida, and Hyalopale cf. bispinosa, from the western and eastern Mediterranean, a smaller form with a similar notochaetal morphology to the latter. Unfortunately, no molecular sequence data is available for Hyalopale bispinosa s.s. Five new species are described, with molecular sequence data provided for three: Hyalopale leslieae sp. nov., a small form with a comparatively low number of paleal ribs, found from the Florida Keys to Belize, Caribbean Sea, H. zerofskii sp. nov. from southern California and Mexico, eastern Pacific and H. sapphiriglancyorum sp. nov., a distinctive species with the lowest number of paleael ribs, from Raja Ampat, Indonesia and the Great Barrier Reef, Queensland, western Pacific. Two other species are described from morphology alone: H. angeliensis sp. nov. from Dampier, Western Australia and Seychelle Islands, eastern Indian Ocean and H. furfuricula sp. nov. from the Red Sea and Mozambique, western Indian Ocean, possessing a unique paleal brow shape. While well supported as a clade, support for relationships within Hyalopale is low. Hyalopale cf. bispinosa (Mediterranean) was recovered as sister group to the remaining Hyalopale, with H. leslieae sp. nov. as sister to the Hyalopale Pacific clade, comprising H. zerofskii sp. nov. (eastern Pacific) and H. sapphiriglancyorum sp. nov. (western Pacific). Within Chrysopetalinae, Hyalopale and Paleanotus formed a clade that was the sister group to the other paleate chrysopetalids under maximum likelihood, though Paleanotus grouped with the other paleate forms under maximum parsimony. The adult morphology of Hyalopale species is compared with that exhibited in the larvae of Paleanotus species; based on these results, including possession of a shared notochaetal character, Hyalopale is considered to contain paedomorphic taxa.