Littoral Sites Research Articles

Sport fish movement responses to a littoral zone coarse woody habitat addition

AbstractObjectiveFish movements and distributions throughout an ecosystem are important for understanding ecological interactions, conservation, and management. Coarse woody habitat (CWH) additions are a popular habitat enhancement tool that can influence movements and distributions of fishes; however, behavioral responses in relation to CWH additions are understudied. The objectives of our study were to test for changes in habitat use and behavioral responses of Muskellunge Esox masquinongy, Smallmouth Bass Micropterus dolomieu, and Walleye Sander vitreus to CWH additions in a small inland northern lake over 3 years and to evaluate two common forms of fish tracking to estimate daily movement of these fishes.MethodsWe used passive integrated transponder tag data collected continuously at 10 littoral sites and radiotelemetry data collected biweekly during the summer–fall months prior (2017) and following (2018–2019) CWH addition to examine movement behaviors and estimate daily probability of movement for the three species among lake habitats using multistate models.ResultWalleye were the most likely to remain near CWH, followed by Smallmouth Bass and Muskellunge. All species were more likely to move away from the modified and unmodified littoral zones and were more likely to remain in the offshore zone. Increased movement of fish may be in response to CWH creating a refuge for forage fish and subsequent increases in prey search times.ConclusionOur results suggest that CWH additions may alter established species‐specific annual movements, distributions, and habitat use to differing degrees in ecosystems, as our results differ from other CWH studies. Methodologically, radio‐tagging was most effective for offshore tracking but most labor intensive. Novel passive integrated transponder arrays (less labor intensive once installed) worked well to monitor movement between habitat types in shallow littoral areas. Long‐term monitoring of behavioral changes will be essential to assessing the stability changes caused by these habitat alterations.

Longevity and efficacy of lanthanum-based P remediation under changing dissolved oxygen availability in a small eutrophic lake.

We set out to study the seasonal variations in porewater phosphorus and lanthanum concentrations in the dated sediment cores from a small eutrophic lake that has been treated with Phoslock, a lanthanum-modified bentonite (LMB) amendment. Three sites were sampled when the hypolimnion was either oxygenated or anoxic: (i) the lake's deepest point, (ii) a littoral site receiving inflows from the catchment, and (iii) a littoral site influenced by nearby septic tanks. Phosphate (PO43--P), lanthanum (La), iron (Fe), dissolved organic carbon (DOC) and sulfate (SO42-) were measured in porewater samples. An inverse diagenetic model was used to quantify fluxes of dissolved elements across the sediment-water interface as well as the net rate of their reactions along the porewater concentration gradients. Results show that porewater P and Fe underwent strong seasonal dynamics, while La did not. P fluxes, 20-fold higher at the deepest site than elsewhere in the basin, were influenced by anoxic conditions in the hypolimnion during summer and winter, suggesting that P mobility remained sensitive to redox fluctuations despite the addition of La. At the deepest site, fluxes of P across the sediment-water interface increased from 1 to 9 × 10-9 μmol cm-2 s-1 between spring and summer, while the rate of P production to the porewater also increased a hundredfold. These increases were concurrent with Fe mobilization. Finally, sediment dating shows that the fraction of P sequestered by La is buried under freshly deposited sediment at a rate of 2-3 mm per year. These results indicate that external P fluxes and erosion control remain crucial to maintain the longevity of the LMB treatment.

Chemical elemental composition of Elodea canadensis Michx. 1791. and its use for the assessment of anthropogenic pollution of the littoral of Lake Baikal

The ICP-MS method was used to study chemical elemental composition of the invasive species Elodea canadensis Michx. at Lake Baikal littoral sites with different degree of anthropogenic load. It is found out that dominant macroelements in E. canadensis are K > Ca > Na > P > Mg > S > Cl, dominant microelements are Fe, Mn > Si, Sr > Al, Ba, Zn > Br, B. The content of Ca, Sr, Mg, B and Si in E. canadensis samples are characterized by the least variability, and Na, P, Cl, K, V, Ni, Cu, Zn, As, Se, Br, Rb, Cd, I, Pb contents are more variable. The maximal heterogeneity in distribution is characteristic for lithophilous elements (Be, Al, Ti, Cr, Mn, Y, Zr, Nb, REE (rare earth), Hf, Ta, W, Th) as well as for Fe, Co, Sn, Sb, Bi. Maximal contents of Na, Cl, K and P associated with income of household waste waters into the near-shore zone is found in Elodea samples collected in Frolikha vent and at littoral sites adjacent to such populated areas as Gremyachinsk, Maksimikha, Nizhneangarsk. The elevated level of Zn, Cd, Pb is characteristic as well for the samples collected at the littoral sites with a high anthropogenic charge (Listvyanka settl., Bugul’deyka, Nizhneangarsk, Maksimikha village and Gremyachinsk).

“Here Be Dragons”: Historical and Contemporary Archaeology and Heritage in the Aegean Sea

Postmedieval, modern, and contemporary remains are ubiquitous, yet their study and curatorship are uncommon in the Aegean geographic context. In this article I discuss the materiality of these uncared-for ruins, drawing from rural and urban remains in the Aegean, contrasted with other littoral sites in the Mediterranean. I focus on their social and cultural impact and their role in contemporary communities, along with the state provisions organized to protect and manage them in Greece and Turkey. I propose a present and socially engaged archaeological praxis and emphasize the need for historical/contemporary archaeology to be more politically involved, raising awareness and broadening the representation of marginalized communities.

Organization of soft soils macrobenthic communities in the littoral of the Chupa Bay of the White Sea: a long-term aspect

The study of interannual changes in the structure of soft soil macrobenthic communities was carried out on the basis of material collected in three littoral sites in the waters of the Keret archipelago of the White Sea in 1983– 2013. The analyzed sites differed in biotopic heterogeneity (characteristics of the soil, degree of closure of water areas, salinity regime). This is a sandy beach in a seaward zone, and two silt-sandy beaches in a semi-enclosed and practically closed water area. The latter is located near the mouth of the Keret River, and is also under the influence of lake runoff, respectively, experiencing a slight freshening. The distance between the sites does not exceed a few kilometers. At two sites, significant changes in the structure of macrobenthos were noted, up to a change in the species dominating in biomass. The study of conjugation of fluctuations in abundance and biomass of common species showed that most taxa demonstrate an independent change in abundance indicators. However, in areas where sea grasses dominated in biomass, the change in the number of significant correlations between taxa, both in abundance and biomass, in some years occurred in accordance with fluctuations in the biomass of Zostera marina Linnaeus, 1753. It was not possible to find climatic and hydrological indicators that would explain the interannual changes in macrobenthos abundance indicators at once in all sites, despite their slight distance from each other. Thus, the conducted studies showed that the structure of macrobenthos of soft soils in the dry zone and the upper sublittoral in the region of the Keret archipelago was distinguished by spatial and temporal heterogeneity, in which one can see a reflection of the biotopic heterogeneity of habitats, features of interspecific relationships, and dynamics of the structure of settlements of dominant species. Under relatively stable climatic, hydrological, and edaphic conditions, significant changes in the structure of the White Sea littoral bottom communities of soft bottoms were mainly determined by natural changes in the structure of settlements of dominant taxa.

Methane Cycle in a Littoral Site of a Temperate Freshwater Lake

Methane Cycle in a Littoral Site of a Temperate Freshwater Lake

Contrasting Dynamics of Littoral and Riparian Reed Stands within a Wetland Complex of Lake Cerknica.

This contribution discusses the use of field measurements and remotely sensed data in an exploration of the effects of environmental parameters on the riparian and littoral stands of the common reed (Phragmites australis) in an intermittent wetland in Slovenia. For this purpose, we created a normalized difference vegetation index (NDVI) time series extending from 2017 to 2021. Data were collected and fitted to a unimodal growth model, from which we determined three different stages relating to the reed's growth. The field data consisted of the above-ground biomass harvested at the end of the vegetation season. Maximal NDVI values at the peak of the growing season exhibited no useful relationship with the above-ground biomass at the end of the season. Intense and long-lasting floods, especially during the period of intense culm growth, hindered the production of common reeds, while dry periods and temperatures were helpful before reed growth began. Summer droughts exhibited little effect. Water level fluctuations exerted a greater effect on reeds at the littoral site due to more pronounced extremes. In contrast, more constant and moderate conditions at the riparian site benefited the growth and productivity of the common reed. These results can prove useful for decision making regarding common reed management at the intermittent lake Cerknica.

Sediment phosphorus composition controls hot spots and hot moments of internal loading in a temperate reservoir

AbstractPhosphorus (P) flux across the sediment–water interface in lakes and reservoirs responds to external perturbations within the context of sediment characteristics. Lentic ecosystems experience profound spatiotemporal heterogeneity in the mechanisms that control sediment P fluxes, likely producing hot spots and hot moments of internal loading. However, spatiotemporal variation in P fluxes remains poorly quantified, particularly in the context of sediment chemistry as a controlling variable. We measured P flux rates and mobile sediment P forms along the longitudinal gradient of a temperate reservoir every 2 months from February to October 2020. Both aerobic and anaerobic processes mobilized sediment P throughout the year. High flux rates at littoral sampling sites (8.4 and 9.7 mg P m−2 day−1) occurred in late summer under oxic conditions in the overlying water and mobilized labile organic P. High fluxes at the profundal site coincided with hypolimnetic anoxia under ice cover and in mid‐summer (11.2 and 17.2 mg P m−2 day−1, respectively) and released redox‐sensitive P. Several high fluxes substantially skewed the flux rate distribution, providing evidence of hot spots and hot moments of internal loading. We further scaled the measured sediment P flux rates to representative areas of the lakebed to estimate internal P loads at an ecosystem scale. We found that P release from littoral sites under oxic conditions in the overlying water had an outsized impact on total loads. Our findings demonstrate the importance of considering spatial and seasonal variation in sediment P pools and fluxes in order to more accurately estimate internal loads and identify the dominant biogeochemical mechanisms involved.

Collaboration, Gender, and Leadership at the Minnesota Seaside Station, 1901–1907

Mentorship and collaboration necessarily shaped opportunities for women in science, especially in the late nineteenth century at rapidly expanding public co-educational universities. A few male faculty made space for women to establish their own research programs and professional identities. At the University of Minnesota, botanist Conway MacMillan, an ambitious young department chair, provided a qualified mentorship to Josephine Tilden. He encouraged her research on algae and relied on her to do departmental support tasks even as he persuaded the administration to move her from instructor to assistant professor in 1903. Resulting publications on Minnesota algae led her to look further west, first at Yellowstone National Park and then along the Pacific Northwest coast. After visiting a particularly productive littoral site on Vancouver Island, she suggested that they establish a Minnesota Seaside Station there. Over its seven years in operation under the Midwestern leaders, that location proved remarkably productive. At the remote site, the two operated within their typical but not inevitable gendered roles and deliberately defined their seaside station as unconventional. They expected participants to study productively and, at the same time, find imaginative ways to enjoy nature at a place far from urban amenities. Gendered expectations remained casual as participants moved both within and against them. This study investigates how, in the early twentieth century, the role and expectations of mentorship shifted as Tilden established her own independent research agenda. The Minnesota Seaside Station, in particular, proved significant in developing the leadership skills essential for her to pursue research in the Pacific region at a time when American expansionism and indigenous cooperation made sites accessible to academic researchers.

Assessing the conservation priority of freshwater lake sites based on taxonomic, functional and environmental uniqueness

AbstractAimWe propose a novel approach that considers taxonomic uniqueness, functional uniqueness and environmental uniqueness and show how it can be used in guiding conservation planning. We illustrate the approach using data for lake biota and environment.LocationLake Puruvesi, Finland.MethodsWe sampled macrophytes and macroinvertebrates from the same 18 littoral sites. By adapting the original “ecological uniqueness” approach, we used distance‐based methods to calculate measures of taxonomic (LCBD–t), functional (LCBD–f) and environmental (LCEH) uniqueness for each site. We also considered the numbers and locations of the sites needed to protect up to 70% of total variation in taxonomic, functional or environmental features in the studied part of the lake.ResultsRelationships between taxonomic (LCBD–t), functional (LCBD–f) and environmental (LCEH) uniqueness were generally weak, and only the relationship between macrophyte LCBD–t and LCBD–f was statistically significant. Overall, however, if the whole biotic dataset was considered, macroinvertebrate LCBD–f values showed a consistent positive relationship with macrophyte LCBD–f. Depending on the measure of site uniqueness, between one‐third to one half of the sites could help protect up to 70% of the ecological uniqueness of the studied part of Lake Puruvesi.Main conclusionsAlthough the dataset examined originated from a large lake system, the approach we proposed here can be applied in different ecosystems and at various spatial scales. An important consideration is that a set of sites has been sampled using the same methods, resulting in species and environmental matrices that can be analysed using the methodological approach proposed here. This framework can be easily applied to grid‐based data, sets of islands or sets of forest fragments. We suggest that the approach based on taxonomic, functional and environmental uniqueness will be a useful tool in guiding nature conservation and ecosystem management, especially if associated with meta‐system ideas or network thinking.

Dynamics of the stream–lake transitional zone affect littoral lake metabolism

Lake ecosystems, as integrators of watershed and climate stressors, are sentinels of change. However, there is an inherent time-lag between stressors and whole-lake response. Aquatic metabolism, including gross primary production (GPP) and respiration (R), of stream–lake transitional zones may bridge the time-lag of lake response to allochthonous inputs. In this study, we used high-frequency dissolved oxygen data and inverse modeling to estimate daily rates of summer epilimnetic GPP and R in a nutrient-limited oligotrophic lake at two littoral sites located near different major inflows and at a pelagic site. We examined the relative importance of stream variables in comparison to meteorological and in-lake predictors of GPP and R. One of the inflow streams was substantially warmer than the other and primarily entered the lake’s epilimnion, whereas the colder stream primarily mixed into the metalimnion or hypolimnion. Maximum GPP and R rates were 0.2–2.5 mg O2 L−1 day−1 (9–670%) higher at littoral sites than the pelagic site. Ensemble machine learning analyses revealed that > 30% of variability in daily littoral zone GPP and R was attributable to stream depth and stream–lake transitional zone mixing metrics. The warm-stream inflow likely stimulated littoral GPP and R, while the cold-stream inflow only stimulated littoral zone GPP and R when mixing with the epilimnion. The higher GPP and R observed near inflows in our study may provide a sentinel-of-the-sentinel signal, bridging the time-lag between stream inputs and in-lake processing, enabling an earlier indication of whole-lake response to upstream stressors.

Indications of polymorphism in the behaviour and morphology of burbot (Lota lota) in a European lake

In this study, polymorphism in behaviour, morphology, and stable isotope signatures of burbot from Lake Southern Konnevesi, Finland, Europe, was examined. First, local knowledge was collected on exceptional polymorphism of the spawning behaviour and morphology of burbot. These phenomena were then studied based on catch samples. Interviews and catch sample analyses suggested two morphs of burbot: one morph spawning in late February in the littoral zone and other in late March, in deep profundal, depths of about 30 m. Fish caught from the profundal zone had higher average proportional somatic body weights and wider heads than those caught from the littoral spawning sites in February. The length-at-age of the individuals from the littoral catch was longer than that of the profundal catch. Stable isotope analysis revealed differences in the mean carbon isotope ratio between sampling sites, suggesting differences in diet. Variability in several of the aforementioned variables was correlated. This study is the first to imply polymorphism in burbot populations from a lake in Eurasia, where burbot are considered as near-threatened species.

Lithic economy in South Western France during the Neolithic: A case study from a coastal site - La Lède du Gurp (Aquitaine)

The prehistory of South-western France is known worldwide for its rich record of Palaeolithic sites, especially from the Dordogne region. However, while research on the Palaeolithic is extremely prolific, the Neolithic was at the same time relegated to the background. Since the beginning of the discipline, few researchers worked on the Neolithic from SW France. Besides, they focused on ceramic typological analyses to describe cultural groups, rarely considered lithic tools and armatures, and never performed any techno-economical study of lithic productions. For over thirty years, rescue archaeology excavations revealed a large presence of Neolithic sites for this period; nonetheless Neolithic research remains little developed in relation to its potential. As part of my PhD thesis, the aim will be to fill this gap by characterizing lithic productions through techno-economical analyses, in order to describe the cultural groups existing in Northern Aquitania during the 4th and the 3rd millennia. With the example of La Lède du Gurp, a littoral occupation site dated to the middle and recent Neolithic, I will try to highlight in this paper what the study of lithic industries can say about a cultural group at a local scale.
 The reconstitution of the operating chains and the statistical analysis of small assemblages of non-standardised lithic reduction, allowed us to highlight a similar low investment in lithic production between the Middle and the Recent Neolithic of La Lède du Gurp. Our approach has enabled us to observe that a low investment in lithic production may reflect the complexity of the Neolithic groups and the complementarity of lithic industry with other technical subsystems directly related with the group's natural environment, as may it be the case for salt production during Recent Neolithic at La Lède du Gurp.

Elevated methylmercury concentration and trophic position of the non-native bloody red shrimp (Hemimysis anomala) increase biomagnification risk in nearshore food webs

The establishment of non-native species can result in complex shifts in food-web structure and ecosystem function that alter the bioaccumulation, transfer, and biomagnification of contaminants. Hemimysis anomala (the bloody red shrimp), a mysid native to the Ponto-Caspian region that is now established throughout the Laurentian Great Lakes region (North America) and Europe, is characterized by high densities and a trophic ecology that may be consequential to mercury fluxes and bioaccumulation. We combined methylmercury (MeHg) and stable isotope (δ15N and δ13C) analyses of invertebrates from Seneca Lake (NY, USA) to test the hypotheses that mercury concentrations differ among (1) H. anomala and native or naturalized analogs due to food-web position and (2) stages of H. anomala due to ontogenetic diet shifts. The MeHg concentration and δ15N of H. anomala exceeded other littoral invertebrates (such as amphipods, dreissenid mussels, and zooplankton >153 μm) and were as high as the pelagic, native Mysis diluviana. These taxa-specific patterns indicate intensified biomagnification of MeHg is possible in nearshore and reef-spawning fish following the establishment of H. anomala, an energy-dense prey item for economically and ecologically important fish. Larger, adult H. anomala had higher MeHg concentrations and more enriched δ15N than juveniles, and H. anomala collected at a littoral site had higher MeHg than a canal site. These intraspecies contrasts are consistent with the shift toward zooplanktivory in adult H. anomala. As both putative prey for fish and competitors for shared zooplankton resources, H. anomala may impact fish in compounding ways.

Succession of aquatic and littoral vegetation in disused sandpits

AbstractVegetation succession in aquatic and littoral environments has received much less attention compared to terrestrial habitats. We sampled differently aged successional stages in 63 sandpits across the Czech Republic, Central Europe. They ranged in age since abandonment from 1 to 64 years. The chronosequence approach was adopted. Besides species identity itself, basic life‐history species traits were considered to describe the succession. Based on the location (elevation) of plots, two geographical regions were delimited based on temperature and precipitation. Alongside the vegetation data, several environmental variables were recorded: age, water depth, substratum type (i.e., proportion of sand, clay, gravel and organic material), pH, conductivity, elevation and additional disturbances. Altogether, 249 vascular plant species were determined. Individual successional series in aquatic and littoral habitats differed between the altitudinal regions. As generally expected, water table was one of the main driving factors alongside age and water conductivity. Moreover, the vegetation pattern was significantly affected by substrate composition and pH. The species composition at aquatic sites was most likely mainly driven by the accumulation of organic material. Hydrophytes dominated throughout these sites. In littoral vegetation, several distinct groups of life forms could be distinguished along the successional gradient. The young sites typically included stress‐tolerant therophytes and hemicryptophytes. With age, woody species started to dominate at littoral sites at higher elevations, while perennial graminoids dominated at lowland sites. Spontaneous succession at aquatic and littoral sites leads to valuable semi‐natural stages and is recommended as a passive restoration option in disused sandpits.

Speleothem Records of the Hydroclimate Variability throughout the Last Glacial Cycle from Manita peć Cave (Velebit Mountain, Croatia)

We present stable carbon (δ13C) and oxygen (δ18O) isotope records from two partially coeval speleothems from Manita peć Cave, Croatia. The cave is located close to the Adriatic coast (3.7 km) at an elevation of 570 m a.s.l. The site experienced competing Mediterranean and continental climate influences throughout the last glacial cycle and was situated close to the ice limit during the glacial phases. U-Th dating constrains the growth history from Marine Isotope Stage (MIS) 5 to MIS 3 and the transition from MIS 2 to MIS 1. 14C dating was used to estimate the age of the youngest part of one stalagmite found to be rich in detrital thorium and thus undatable by U-Th. On a millennial scale, δ18O variations partly mimic the Dansgaard–Oeschger interstadials recorded in Greenland ice cores (Greenland Interstadials, GI) from GI 22 to GI 13. We interpret our δ18O record as a proxy for variations in precipitation amount and/or moisture sources, and the δ13C record is interpreted as a proxy for changes in soil bioproductivity. The latter indicates a generally reduced vegetation cover towards MIS 3–MIS 4, with shifts of ~8‰ and approaching values close to those of the host rock. However, even during the coldest phases, when a periglacial setting and enhanced aridity sustained long-residence-time groundwater, carbonic-acid dissolution remains the driving force of the karstification processes. Speleothem morphology follows changes in environmental conditions and complements regional results of submerged speleothems findings. Specifically, narrow sections of light porous spelaean calcite precipitated during the glacial/stadial sea-level lowstands, while the warmer and wetter conditions were marked with compact calcite and hiatuses in submerged speleothems due to sea-level highstands. Presumably, the transformation of this littoral site to a continental one with somewhat higher amounts of orographic precipitation was a site-specific effect that masked regional environmental changes.

Aquatic biofilms can act as natural environmental DNA samplers

Diatoms, macroinvertebrates and fish communities are widely used for the assessment of the ecological status of rivers and lakes. Metabarcoding studies of these communities are usually performed from “bulk” samples in the case of diatoms and macroinvertebrates; and from water samples in the case of fish. Recent studies, suggest that aquatic biofilms can physically act as environmental catchers of environmental DNA (eDNA) (e.g. Mariani et al. 2019). Thus, we propose an alternative metabarcoding approach to study macroinvertebrates and fishes directly from this matrix. The capacity of aquatic biofilms to catch macroinvertebrate eDNA was tested from a previous study in Mayotte Island were both biofilm samples and macroinvertebrate morphological inventories were available at same river sites (Rivera et al. 2021). First, macroinvertebrate specimens were identified based on their morphological characteristics. Second, DNA was extracted from biofilms, and macroinvertebrate communities were targeted using a standard COI barcode. The resulting morphological and molecular inventories were compared. Our results showed that both methods provided comparable structures and diversities for macroinvertebrate communities when using unassigned OTUs suggesting that macroinvertebrate DNA is present in biofilms and representative of the communities. However, after taxonomic assignment of OTUs, diversity and richness were no longer correlated. Indeed, many constraints were observed as the need for: a) more specific primers to avoid co-amplification of untargeted taxa inhabiting biofilms, b) primers targeting shorter barcodes to sequence more easily degraded eDNA that may be captured in biofilms, and c) a reference database well adapted to our tropical study sites. Finally, even if the results of this first study were encouraging, we wanted to test the biofilm approach on organisms that do not inhabit this environmental matrix in order to be able to distinguish between intra or extra-cellular DNA. Based on these observations, a second study looking for a fish eDNA signal in aquatic biofilms was performed. Environmental biofilm and water samples were collected in parallel at littoral sites at Lake Geneva. DNA was extracted from these samples, and fish communities were targeted using a standard 12S barcode. The molecular inventories derived from the biofilm and the water samples were compared. Both methods provide comparable floristic lists, providing a novel approach for ecological studies related to fish phenology using eDNA in biofilms. Our results open the door to the study of diatoms, macroinvertebrates and fish communities through metabarcoding from a single matrix reducing sampling efforts and costs.

A month for the mission: using a sentinel approach to determine the transmission window of digenean cercariae in the subarctic White Sea.

In the digenean life cycle the cercaria ensures an important transmission stage, from the first intermediate host to the second or the definitive host. In regions with pronounced seasonality, this process occurs within a certain interval, the transmission window. In high latitudes, the size of transmission window has previously been determined only by comparing data on seasonal dynamics of infection level in various categories of hosts or extrapolating the results of laboratory experiments on cercarial biology to natural conditions. In this study, we evaluated the dynamics of infection of the second intermediate hosts (mussels Mytilus edulis) with cercariae of two digenean species, Himasthla elongata (Himasthlidae) and Cercaria parvicaudata (Renicolidae), at a littoral site at the White Sea by exposing cages with uninfected mussels during the warm season. This is the first such study in a subarctic sea. Mussel infection was observed from May to mid-September, but its intensity was the greatest only for approximately a month, from some moment after 10 July to mid-August, when water temperature was within the optimal range for cercarial emergence in both studied species (15‒20°C). During this time, the mussels accumulated 66.3 ± 6.2% metacercariae of H. elongata and 79.7 ± 5.3% metacercariae of C. parvicaudata out of the total number accumulated during the experimental period. We suggest that climate warming at high latitudes may prolong the period when the water temperatures are optimal for cercariae emergence, thereby intensifying digenean transmission in coastal ecosystems.

Zooplankton community changes in relation to different macrophyte species: Effects of Egeria densa removal

Macrophytes sometimes become a nuisance, interfering with navigation, fishing, and aesthetic purposes. Therefore, in many water bodies, the macrophytes are periodically removed. However, with the removal of macrophytes, changes occur in the physico-chemical properties of water and the plankton associated with them. Here we describe the zooplankton community composition using functional traits (feeding guilds and habitat type) from littoral and open water zones in the central Mexican waterbody Benito Juárez Reservoir for one year. In two sites, the macrophyte Egeria densa was removed by the local administration, which resulted in an increase of turbidity, chlorophyll a and phycocyanin levels. Among rotifers, Polyarthra, Trichocerca, Lecane, Lepadella, and Keratella were the dominant genera while for microcrustaceans, copepods, Alona, Ceriodaphnia, Chydorus, and Simocephalus were the dominant genera. Littoral sites had a higher number of microphagous and raptorial species than open water; however, after macrophyte removal, microphagous species were more reduced than raptorial species. Moreover, a decrease in semi-planktonic and benthic-periphytic species, as well as an increase in planktonic organisms was observed after macrophyte removal. Nonmetric multidimensional scaling showed that before the removal of Egeria, macrophyte sites were different from open water; however, after the removal, the zooplankton community was similar in all sites. Canonical correspondence analysis (CCA) showed that carbonates, nitrates, oxygen, and turbidity were the strongest predictors determining zooplankton composition. Our study showed that macrophyte removal caused habitat modification and zooplankton community shifts that reduce diversity and functional groups.

Assessment of seasonal variation in physico-chemical characteristics of a lentic waterbody of Bhopal, India

The present study was conducted with an aim to assess the seasonal variation and nutrient status of a lentic water body (Lower lake) of Bhopal, India. Different variables involving water temperature (W.T), Secchi transparency (TRN), pH, total dissolved solids (TDS), conductivity (CON), total alkalinity (T.A), dissolved oxygen (DO), chlorides (CL), total hardness (TH), orthophosphate (PO4-3) and nitrate (NO3-N) were examined using the standard methodology of APHA (2005). Significant seasonal variation was observed in Secchi transparency which ranged from 27 cm to 83 cm, chlorides (29 mg/l to 58 mg/l, dissolved oxygen (1.6 mg/l to 9.2 mg/l), phosphate (1.76 mg/l to 2.9 mg/l) and nitrate (0.98 mg/l to 3.57 mg/l). Our results confer that the water body is undergoing nutrient enrichment especially littoral sites due to direct influx of untreated sewage from surrounding urban settlements which has resulted in the deterioration of water quality of the lake. Pearson correlation analysis was employed to determine the relationship among water parameters which revealed both significant positive and negative trends.