Littoral Habitats Research Articles

Habitat utilization and feeding ecology of small round goby in a shallow brackish lagoon

We examined small-scale distribution and feeding ecology of a non-native fish species, round goby (Neogobius melanostomus (Pallas, 1814)), in different habitats of a coastal lagoon situated in the south-western Baltic Sea. First observations of round goby in this lagoon were reported in 2011, 3 years before the current study was conducted, and information on this species’ basic ecology in different habitats is limited. We found that mainly juvenile round gobies are non-randomly distributed between habitats and that abundances potentially correlate positively with vegetation density and thus structural complexity of the environment. Abundances were highest in shallower, more densely vegetated habitats indicating that these areas might act as a refuge for small round gobies by possibly offering decreased predation risk and better feeding resources. Round goby diet composition was distinct for several length classes suggesting an ontogenetic diet shift concerning crustacean prey taxa between small (≤ 50 mm total length, feeding mainly on zooplankton) and medium individuals (51–100 mm, feeding mainly on benthic crustaceans) and another diet shift of increasing molluscivory with increasing body size across all length classes. Differences in round goby diet between habitats within the smallest length class might potentially be related to prey availability in the environment, which would point to an opportunistic feeding strategy. Here, we offer new insights into the basic ecology of round goby in littoral habitats, providing a better understanding of the ecological role of this invasive species in its non-native range, which might help to assess potential consequences for native fauna and ecosystems.

Riparian forest subsidises the biomass of fish in a recently formed subtropical reservoir

AbstractRiparian forest may represent a key subsidy to aquatic food webs. While most research has been done in running waters, the origin of resources subsidising biomass and the role of riparian coverage in food webs remains largely unstudied in reservoirs. This research evaluated the role of forest riparian zones as food web subsidies in a recently formed reservoir of Ijuí River, Brazil. The diet of fish and the origin of carbon and nitrogen fuelling fish biomass was compared between littoral habitats with riparian forests and of open canopy. Sampling for stable isotopes of fish and basal resources and the application of bayesian mixing models showed that most of the fish production originates from terrestrial carbon in this recently formed reservoir. Moreover, an increasing terrestrial support to the biomass was found towards the riparian forest areas (subsidising c.a. 70% vs. around 57% of fish biomass in littoral areas of riparian forest and open canopy, respectively).This study remarked the role of riparian forest areas as energetic subsidises to aquatic ecosystems. Management actions in newly formed reservoirs should include preserving riparian forests to avoid losing natural ecosystem subsidies.

Disappearance Rates of a Placebo Bait for the Small Indian Mongoose Across Different Habitats on St. Kitts

The small Indian mongoose (Urva aurpunctata) is a non-indigenous wildlife reservoir for rabies virus on several Caribbean islands. Oral rabies vaccination (ORV) has been suggested to prevent the spread of rabies in mongooses, but there are limited data on ORV bait survival in maritime/tropical climates. We compared disappearance rates of an egg-flavored bait block vs. a control (canned tuna) and for bait blocks, we assessed if season, habitat, and day/night would influence the disappearance rate. On the island of St. Kitts, West Indies, we baited 45 stations (n=35 bait blocks, n=10 controls) at dawn and checked them twice daily for 4 consecutive days. This procedure was repeated after a two-day period, for each combination of season (dry and wet) and habitat type (mixed grassland, littoral and dry forest). We used the Kaplan-Meier method to estimate bait survival at 12 and 36 hours after baiting. Across all sites, control baits were removed faster than bait blocks, but by 36 hours, over 90% of all baits had disappeared. For bait blocks only, the disappearance rate was higher during the dry season and in the dry forest habitat compared to the other habitats. There was no difference between diurnal and nocturnal disappearance rates. While the exact species that consumed the baits remain uncertain, we found that mongooses readily remove bait blocks, along with non-native mammals (e.g., dogs and cats) and land crabs in littoral habitats. We suggest that the bait blocks used in this study may be suitable for use as an external bait matrix for ORV baits.

Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm

For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.

Ecosystem response to earlier ice break-up date: Climate-driven changes to water temperature, lake-habitat-specific production, and trout habitat and resource use.

Climate warming has yielded earlier ice break-up dates in recent decades for lakes leading to water temperature increases, altered habitat, and both increases and decreases to ecosystem productivity. Within lakes, the effect of climate warming on secondary production in littoral and pelagic habitats remains unclear. The intersection of changing habitat productivity and warming water temperatures on salmonids is important for understanding how climate warming will impact mountain ecosystems. We develop and test a conceptual model that expresses how earlier ice break-up dates influence within lake habitat production, water temperatures and the habitat utilized by, resources obtained and behavior of salmonids in a mountain lake. We measured zoobenthic and zooplankton production from the littoral and pelagic habitats, thermal conditions, and the habitat use, resource use, and fitness of Brook Trout (Salvelinus fontinalis). We show that earlier ice break-up conditions created a "resource-rich" littoral-benthic habitat with increases in zoobenthic production compared to the pelagic habitat which decreased in zooplankton production. Despite the increases in littoral-benthic food resources, trout did not utilize littoral habitat or zoobenthic resources due to longer durations of warm water temperatures in the littoral zone. In addition, 87% of their resources were supported by the pelagic habitat during periods with earlier ice break-up when pelagic resources were least abundant. The decreased reliance on littoral-benthic resources during earlier ice break-up caused reduced fitness (mean reduction of 12g) to trout. Our data show that changes to ice break-up drive multi-directional results for resource production within lake habitats and increase the duration of warmer water temperatures in food-rich littoral habitats. The increased duration of warmer littoral water temperatures reduces the use of energetically efficient habitats culminating in decreased trout fitness.

Ecological consequences of shoreline armoring on littoral fish and benthic macroinvertebrate communities in an Eastern Ontario lake

Shoreline erosion in lakes is a pressing issue for many landowners, yet common erosion mitigation practices that involve armoring can alter littoral habitat and potentially diminish near-shore biodiversity. We studied the effects of two armoring methods (i.e., riprap, retaining walls) on habitat, taxonomic richness, relative abundance, and total abundance of fishes and benthic macroinvertebrates at shorelines on Big Rideau Lake in eastern Ontario, Canada. Snorkel surveys were conducted to assess aquatic habitat characteristics and fish diversity, and benthic infauna were sampled using kick-nets. Submergent and emergent macrophytes were more abundant at natural rocky shorelines compared to shorelines modified with riprap or retaining walls. Coarse woody debris was also more abundant at natural shorelines compared to riprap and retaining wall shorelines. Relative abundances of some fish species varied between shoreline types, but overall species richness and total abundance did not. Largemouth Bass (Micropterus salmoides) were more abundant at natural sites than armored sites. Conversely, Rock Bass (Ambloplites rupestris), Pumpkinseed (Lepomis gibbosus), Bluegill (Lepomis macrochirus), Yellow Perch (Perca flavescens), and baitfish from the family Cyprinidae were more abundant at both types of armored sites compared to natural sites. Taxonomic richness of benthic macroinvertebrates did not vary among shoreline types, however abundance of Amphipoda, Isopoda, Ephemeroptera, and Cladocera was greater at armored shorelines. These results suggest that human modification of shorelines is altering littoral ecosystems and potentially leading to shifts in the community structure of littoral nekton. More study is needed to fully understand the community level effects of shoreline erosion mitigation involving armoring in freshwater lakes and determine the effectiveness of alternative mitigation strategies that preserve natural habitat features.

Nutritional quality of littoral macroinvertebrates and pelagic zooplankton in subarctic lakes

AbstractLittoral benthic primary production is considered the most important energy source of consumers in subarctic lakes. We analyzed essential fatty acid (EFA) and amino acid (EAA) content of 23 littoral benthic macroinvertebrate taxa as well as cladocerans and copepods from pelagic and littoral habitats of 8–9 subarctic lakes to compare their nutritional quality. Pelagic crustacean zooplankton had significantly higher EFA and total FA content (on average 2.6‐fold and 1.6‐fold, respectively) than littoral macroinvertebrates in all our study lakes. Specifically, docosahexaenoic acid (DHA), one of the most important EFA for juvenile fish, was almost exclusively found in pelagic copepods. In littoral macroinvertebrates, only Lymnaea (Gastropoda), Eurycercus (Cladocera), and Gammarus (Amphipoda) contained a low amount of DHA, whereas most littoral invertebrate taxa contained moderate amounts of eicosapentaenoic acid (EPA). The difference in DHA content may explain why so many generalist fish shift their diet to pelagic zooplankton at their peak abundance in mid/late‐summer. Meanwhile, the differences in EAA content between pelagic zooplankton and littoral invertebrates were much lower than for EFA suggesting a wider availability of EAA in subarctic lakes, except for methionine. In the studied subarctic lakes, EFA and EAA variation in consumers was more related to taxon‐specific than lake‐specific characteristics. This indicates that climate‐induced changes in the abundance and community structure of zooplankton vs. littoral macroinvertebrates will be important parameters in determining the availability of EFA and EAA to juvenile fish, and potentially fish production.

Trophic dynamics of a reservoir fishery following an introduction of a top predator: Insights from stable carbon and nitrogen isotopes

AbstractTrophic dynamics and conceptual niche spaces of top piscivores were assessed using stable isotope analysis following the introduction of hybrid striped bass Morone saxatilis (Walbaum) × Morone chrysops (Rafinesque) into an established reservoir fishery devoid of gizzard shad, Dorosoma cepedianum (Lasueur). Hybrid striped bass were initially stocked into Three Mile Lake, Iowa as an attempt to biologically control pervasive yellow bass, Morone mississippiensis Jordan & Eigenmann, populations. From the analyses, it concluded that hybrid striped bass predominately targeted prey fish located in the littoral habitats of the reservoir and did not selectively consume yellow bass as intended. Bayesian isotope mixing models described the diets of hybrid striped bass to include a variety of prey fish, predominantly consisting of young bluegill Lepomis macrochirus and yellow bass. Food resource overlap among hybrid striped bass, largemouth bass, Micropterus salmoides Lacépède, and walleye, Sander vitreus (Mitchill), appeared substantial based on the isotopic niche overlap model. Results from this case study, in conjunction with the hindsight that yellow bass populations became prolific even with stockings of hybrid striped bass, suggest that their use to control yellow bass populations may not be a viable management strategy in southern Iowa.

A remarkable new genus and species of Hansenauropodidae (Myriapoda, Pauropoda) from the seashore of Hainan Island, China.

Psammopauropus macrospinus gen. et sp. n., a remarkable new genus and species of the pauropod family Hansenauropodidae is described from the marine littoral habitat of Hainan Island, South China. It has one pair of dorsal spines on the pygidium differentiated from seta a1, large globular seta st on pygidium, and globular distal setae on the tarsi by which Psammopauropus can be easily distinguished from all other genera of the family. In addition, the adaptive characters of the littoral pauropods are preliminary discussed. This is the first record of the family Hansenauropodidae from China.

Impacts of ontogenetic dietary shifts on the food-transmitted intestinal parasite communities of two lake salmonids.

Ontogenetic dietary shifts are common in fish and often impact trophically transmitted parasite communities. How parasite species composition and relative abundances change among size classes, and at what rate these changes occur, is rarely examined. Hosts with a broad trophic niche are potentially exposed to a large variety of parasite species. The degree of ontogenetic changes in parasite species composition versus changes in parasite abundance should suggestively differ between thropically generalist and specialist host species. In the present study, we explore ontogenetic dietary shifts and their impact on species composition and relative abundance of intestinal parasites in two sympatric salmonid fish species, Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) caught in the littoral habitat of a subarctic lake. Our results highlight a close interplay between ontogenetic dietary niche shifts and alterations in the acquisition of trophically transmitted parasites, leading to host-specific differences in the component community of parasites. Ontogenetic changes in the intestinal parasite community related to dietary niche shifts were distinct but less pronounced in Arctic charr than in brown trout due to a broader and more consistent dietary niche of the former and an ontogenetic shift toward piscivory in the latter. At the component community level, changes in parasite assemblages of both host species were driven by a faster increase in the heterogeneity of parasite relative abundance than in the compositional heterogeneity, a pattern that partly may be related to a rather species-poor parasite community of this subarctic study system. Separating compositional heterogeneity from heterogeneity in relative parasite abundance is important to understand how size-dependent variability shapes parasite communities of host populations.

The relative influence of the environment, land use, and space on the functional and taxonomic structures of phytoplankton and zooplankton metacommunities in tropical reservoirs

Disentangling the effects of space and the environment on species distribution is one of the current goals of ecology and biogeography. In this study, we aimed to determine the relative influence of local, spatial (directional and non-directional), and land-use predictors on the taxonomic and functional trait compositions of phytoplankton and zooplankton assemblages. We collected data from 25 sampling points within shallow artificial water reservoirs in the central-western region of Brazil. This study was conducted in an area with a small spatial extent (<50 km between sampling sites) and in a reservoir of a typical hierarchical branching river network. The explanatory variables included 8 environmental features, 2 land-use predictors, and 2 spatial proxies (non-directional and directional spatial eigenvectors). We used a partial redundancy analysis to evaluate the relative influence of each predictor. Only spatial predictors, mainly directional, were important in explaining the phytoplankton and zooplankton metacommunity structure (functional and taxonomic). According to the metacommunity perspective, our results indicated that the phytoplankton and zooplankton metacommunities could be classified as species sorting with high dispersal, that is, a mass-effect perspective. We expected to see mass-effect processes in our study area, in which highly-dispersive species occur in a small-scale, highly-connected area where upstream reservoirs act as sources for dispersing species downstream. Moreover, some functional traits and morphofunctional attributes of phytoplankton (presence of flagella and small size) and zooplankton (suspensivore, carnivore, and littoral habitats) were associated with an increase in dispersal. Finally, this study contributes to the understanding of how environment, space, and land-use components structure plankton metacommunities.

Subfossil Simuliidae track past river flow into an industrially contaminated lake

Stoco Lake (Tweed, Ontario, Canada) has a history of industrial contamination and is heavily influenced by inflow from the Moira River. Stoco Lake is frequently affected by nuisance algal blooms (including cyanobacteria), which have largely been attributed to cultural eutrophication. To further our understanding of the environmental dynamics of Stoco Lake, we applied paleolimnological techniques to examine long-term trends in subfossil invertebrate assemblages, geochemistry, and inferred trends in whole-lake primary production from a sediment core representing ~ 70 years of environmental history. We examined past trends in Simuliidae abundance, geochemical variables, and historical river flow records to examine past hydrological conditions in Stoco Lake. Inferred whole-lake primary production and sediment core organic content increased between the late 1950s and early 1970s, likely reflecting increased eutrophication (e.g. from agricultural intensification and increased catchment activities), with some stabilization in the post-1970s sediments coinciding with the installation of a sewage treatment plant. The geochemical composition of the core highlighted the decrease in catchment-derived sediment inputs and an increase in percentage of organic content towards the top of the core. In addition, declines in the proportion of As and Ni coincided with the closure of the upstream Deloro Mine Site in the 1960s. Chironomidae and Chaoboridae (Diptera) assemblages indicate expansion of littoral habitat after the 1960s and a general stability of low-oxygen conditions in the hypolimnion over the past ~ 70 years. Several Simuliidae (Diptera: Nematocera) remains, indicators of fluvial conditions rarely discussed in paleolimnological studies, were present at their highest abundances in the pre- ~ 1975 sediments of the core, but disappeared after the early 1990s. Our findings suggest that changes in river flow (discharge, velocity, or seasonality) may have contributed to recent algal blooms. Overall, this study highlights the potential of Simuliidae in paleohydrological studies to help understand the role of river flow on lake conditions.

Regulation of fatty acid composition related to ontogenetic changes and niche differentiation of a common aquatic consumer

Fatty acids (FAs) are key nutrients for fitness which take part in multiple physiological processes over the ontogeny of organisms. Yet, we lack evidence on how FA nutrition mediates life-history trade-offs and ontogenetic niche shifts in natural populations. In a field study, we analyzed ontogenetic changes in the FAs of Eurasian perch (Perca fluviatilis L.), a widespread fish that goes through ontogenetic niche shifts and can have high individual niche specialization. Diet explained most of the variation in the FA composition of perch dorsal muscle over early ontogeny (28%), while the total length explained 23%, suggesting that perch significantly regulated FA composition over early ontogeny. Condition explained 1% of the remaining variation. 18:3n-3 (ALA) and 18:4n-3 (SDA) indicated planktivory; 18:1n-7, benthivory; and 22:6n-3 (DHA), piscivory in perch diet. Conversely, perch regulated long-chained polyunsaturated fatty acids (PUFAs), such as 20:5n-3 (EPA), 20:4n-6 (ARA) and 22:6n-3 (DHA) over ontogeny, emphasizing the role of such FAs in early growth and sexual maturation. Adult perch increasingly retained 16:1n-7 and 18:1n-9 suggesting higher energy storage in older perch. Furthermore, differences in DHA availability in diet correlated with intra-cohort differences in perch growth, potentially hindering the overall use of benthic resources and promoting earlier shifts to piscivory in littoral habitats. Overall, this study indicates that in addition to diet, internal regulation may be more important for FA composition than previously thought. Differences between FA needs and FA availability may lead to life-history trade-offs that affect the ecology of consumers, including their niche.

Temporal Scaling of Water Level Fluctuations in Shallow Lakes and Its Impacts on the Lake Eco-Environments

Managing lake water levels from an ecological perspective has become an urgent issue in recent years in efforts to protect, conserve, and restore lake eco-environments. In this study, we considered the actual situation of Ebinur Lake basin to develop a lake water balance model using a System Dynamics (SD) method. The objective of this study is based on the lake water balance model to sufficiently understand the variation and relationship between the lake depth–area–volume. We combined field investigations and hydrological data analysis to expose the major factors affecting lake water level fluctuations (WLFs), as well as the impact of WLFs on lake eco-environments. All with the aim of providing a theoretical basis to manage Ebinur Lake ecosystems for conservation and restoration. The main findings of this study include: (I) The model’s calculation results agree with the observation value, as the monthly lake surface area was used to validate the model. (II) The factors influencing the dynamic changes in the water level of the lake are ranked in ascending order (from the lowest to the highest) as follows: Precipitation, groundwater recharge, evaporation, river inflow. (III) Fluctuations in water level play a significant role in lake shoreline displacement variation, and when the lake’s water level drops below 1 m, the surface area of the water body decreases to approximately 106 km2. (IV) The magnitude and frequency of WLFs drive major differences in the ecology of lake littoral zones, influencing not only the structure and functioning of benthic assemblages but also littoral habitat structure. These results established a quantitative linkage between hydrological variables and ecosystem health for the Ebinur Lake wetlands. These findings could be widely used in managing the Ebinur Lake basin as well as other similar water bodies, and could provide a useful tool for managing lake ecosystems for conservation and restoration.

Low connectivity between sympatric populations of sunfish ecotypes suggests ecological opportunity contributes to diversification

Ecological opportunities, such as access to a novel habitat or the extirpation of a key competitor, can lead to adaptive divergence by exposing populations to diversifying selection. Typically, effects of ecological opportunity on adaptive divergence are inferred from macroevolutionary patterns rather than tested in populations undergoing contemporary divergence. This limits our insight on how ecological conditions contribute to adaptive divergence. Pumpkinseed sunfish (Centrarchidae: Lepomis gibbosus) have recently and repeatedly colonized a ‘novel’ pelagic habitat in postglacial lakes, and subsequently undergone phenotypic diversification. We investigated whether ecological opportunity has contributed to diversification in a pumpkinseed population that has diversified between lake habitats. We used a between-year mark-recapture study to evaluate whether (1) the novel pelagic habitat represents an ecological opportunity by supporting a large, high-density population, and (2) connectivity between ecotype populations is restricted by limited adult dispersal. We found that phenotypic variation is spatially structured between habitats, similar to prior studies. Submerged shoals in the pelagic habitat do sustain a large adult population at a density seven times greater than the ancestral littoral habitat. Additionally, body condition and size of pelagic pumpkinseed is similar to littoral pumpkinseed. This suggests the pelagic habitat provides an ecological opportunity to pumpkinseed in the form of abundant, available resources. Furthermore, strong between-year habitat fidelity suggests aspects of the ecological opportunity have reduced adult dispersal and could limit gene flow. In combination with prior evidence indicating diversifying selection between habitats, these results provide an example of how ecological opportunity might contribute to contemporary adaptive divergence.

The Tumblagooda Sandstone revisited: exceptionally abundant trace fossils and geological outcrop provide a window onto Palaeozoic littoral habitats before invertebrate terrestrialization

AbstractThe establishment of permanent animal communities on land was a defining event in the history of evolution, and one for which the ichnofauna and facies of the Tumblagooda Sandstone of Western Australia have been considered an archetypal case study. However, terrestrialization can only be understood from the rock record with conclusive sedimentological evidence for non-marine deposition, and original fieldwork on the formation shows that a marine influence was pervasive throughout all trace fossil-bearing strata. Four distinct facies associations are described, deposited in fluvial, tidal and estuarine settings. Here we explain the controversies surrounding the age and depositional environment of the Tumblagooda Sandstone, many of which have arisen due to the challenges in distinguishing marine from non-marine depositional settings in lower Palaeozoic successions. We clarify the terminological inconsistency that has hindered such determination, and demonstrate how palaeoenvironmental explanations can be expanded out from unambiguously indicative sedimentary structures. The Tumblagooda Sandstone provides a unique insight into an early Palaeozoic ichnofauna that was strongly partitioned by patchy resource distribution in a littoral setting. The influence of outcrop style and quality is accounted for to contextualize this ichnofauna, revealing six distinct low-disparity groups of trace fossil associations, each related to a different sub-environment within the high-ichnodisparity broad depositional setting. The formation is compared with contemporaneous ichnofaunas to examine its continued significance to understanding the terrestrialization process. Despite not recording permanent non-marine communities, the Tumblagooda Sandstone provides a detailed picture of the realm left behind by the first invertebrate pioneers of terrestrialization.

Seasonal dietary shifts enhance parasite transmission to lake salmonids during ice cover.

Changes in abiotic and biotic factors between seasons in subarctic lake systems are often profound, potentially affecting the community structure and population dynamics of parasites over the annual cycle. However, few winter studies exist and interactions between fish hosts and their parasites are typically confined to snapshot studies restricted to the summer season whereas host‐parasite dynamics during the ice‐covered period rarely have been explored. The present study addresses seasonal patterns in the infections of intestinal parasites and their association with the diet of sympatric living Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) in Lake Takvatn, a subarctic lake in northern Norway. In total, 354 Arctic charr and 203 brown trout were sampled from the littoral habitat between June 2017 and May 2018. Six trophically transmitted intestinal parasite taxa were identified and quantified, and their seasonal variations were contrasted with dietary information from both stomachs and intestines of the fish. The winter period proved to be an important transmission window for parasites, with increased prevalence and intensity of amphipod‐transmitted parasites in Arctic charr and parasites transmitted through fish prey in brown trout. In Arctic charr, seasonal patterns in parasite infections resulted mainly from temporal changes in diet toward amphipods, whereas host body size and the utilization of fish prey were the main drivers in brown trout. The overall dynamics in the community structure of parasites chiefly mirrored the seasonal dietary shifts of their fish hosts.

Post-glacial lake development and paleoclimate in the central Hudson Bay Lowlands inferred from sediment records

We compile a multi-proxy Holocene record from North Raft Lake located in the sub-Arctic Hudson Bay Lowlands, Canada. Specifically, we use subfossil chironomid, diatom, and pollen assemblages, non-pollen palynomorphs, sedimentary chlorophyll a, magnetic susceptibility, and organic matter content to characterize terrestrial and lake processes and to track paleoclimate following land emergence from the postglacial Tyrrell Sea. Following recession of the Tyrrell Sea (~ 6600 cal yr BP), pollen assemblages are indicative of a salt marsh environment with the establishment of an opportunistic chironomid assemblage. By ~ 6200 cal yr BP, isostatic uplift reduced the marine influence and pollen and palynomorph assemblage changes indicate that North Raft Lake became a closed-basin freshwater system. At this time, pollen assemblages signify the establishment of a forested peatland dominated by Picea, and chironomid taxa indicate warming water temperatures. The North Raft Lake pollen/palynomorph record captures a warm and moist mid-Holocene (Holocene Thermal Maximum) period starting ~ 6200 cal yr BP. During this period, an increase in pollen concentration and a shift to higher abundances of Larix indicate watershed-scale succession and enhanced local ecosystem productivity. Shifts in chironomid taxa at ~ 5000 cal yr BP are indicative of abrupt limnological changes suggesting wet conditions that caused an expansion of littoral habitat. The gradual transition into Neoglacial cooling is signaled by an increase in the abundances of cold-stenothermal chironomid taxa and a small decline in pollen-reconstructed temperatures. Marked changes occur in the mid-twentieth century with the appearance of diatoms in notable abundances for the first time in the lake’s sedimentary record, the arrival of new chironomid littoral taxa, and unprecedented increases in sedimentary chlorophyll a and organic matter content. Throughout the North Raft Lake Holocene sediment record, the pollen trends suggest slow centennial-scale changes in temperature and precipitation, whereas chironomid assemblages indicate abrupt mid-Holocene and twentieth century limnological changes, stressing that biota in lakes of the Hudson Bay Lowlands may change substantially under future scenarios of global climate warming.

Habitat use by early life stages of the re-established striped bass and conspecific fish species along the St. Lawrence estuary

The St. Lawrence estuary (SLE) supports important nursery habitats for many fish species, including the newly re-established population of striped bass (Morone saxatilis).The present study aims to describe pelagic (5 m isobaths) and littoral (<1.5 m-deep) nearshore habitats of the SLE and to document their use by fish larvae and age-0 juveniles, especially for striped bass. From June to September 2014, 162 pelagic and 188 littoral stations were characterized in terms of biophysical conditions (turbidity, salinity, temperature, dissolved oxygen and chlorophyll-a concentration), abundance of main preys and fish assemblages. Striped bass larvae identification was confirmed with genetic analyses. In the pelagic and littoral zones, four estuarine habitats were defined based on turbidity and salinity: an upstream freshwater section (UP), an oligohaline (O-ETM) and a mesohaline (M-ETM) estuarine turbidity maximum zone, and a downstream polyhaline section (DOWN). Our results emphasized the spatial partitioning of fish early life stages among contrasting habitats, potentially to minimize interspecific competition. In the SLE, striped bass is using the wide spectrum of habitats available. At the onset of striped bass development, the UP and the O-ETM were the main nursery habitats, which is consistent with the known location of spawning grounds. Results suggest that the O-ETM provided the most suitable conditions for the species with optimal physical properties and abundant food resources. Later in the season, the M-ETM provided a favourable trade-off habitat offering a less optimal physical environment although potential for new prey.

Ecological impact of land reclamation on Jiangsu coast (China): A novel ecotope assessment for Tongzhou Bay

China's continuous and rapid economic growth has led to the reclamation of large sections of the intertidal mud coast in combination with port construction, such as that of the proposed Tongzhou Bay port on the Jiangsu coast. These reclamations threaten the local ecosystem services. An ecotope distribution map was created and a hydrodynamic numerical model of Tongzhou Bay was set up to quantify the impacts of reclamation on the ecosystem. Based on the field data and model results, several abiotic features were classified into 11 ecotopes and visualized in an ecotope map of the Tongzhou Bay ecosystem. Validation with spatial distributions of two threatened shorebird species (bar-tailed godwit and great knot) showed confirmation with the mid-range and low-range littoral zones (inundated from 40% to 100% of a tidal cycle), indicating the importance of the areas with these conditions to these populations. Overlaying the ecotope map with recent and proposed land reclamation schemes revealed a loss of ecotopes, composed of the high-range (42%), mid-range (48%), and low-range (38%) littoral habitats, corresponding to a 44%–45% loss of the most important ecotopes for bar-tailed godwit and great knot (mid-range and low-range littoral zones). These results confirm the applicability of the novel ecotope assessment approach in practice.