AimBiogenic structural complexity increases mobile animal richness and abundance at local, regional and global scales, yet animal taxa vary in their response to complexity. When these taxa also vary functionally, habitat structures favouring certain taxa may have consequences for ecosystem function. We characterised global patterns of epifaunal invertebrates in eelgrass (Zostera marina) beds that varied in structural and genetic composition.LocationNorth America, Europe and Asia.Time Period2014.Major Taxa StudiedPeracarid crustaceans and gastropod molluscs.MethodsWe sampled epifaunal invertebrate communities in 49 eelgrass beds across 37 degrees latitude in two ocean basins concurrently with measurements of eelgrass genetic diversity, structural complexity and other abiotic and biotic environmental variables. We examined how species richness, abundance and community composition varied with latitude and environmental predictors using a random forest approach. We also examined how functional trait composition varied along with community structure.ResultsTotal species richness decreased with latitude, but this was accompanied by a taxonomic shift in dominance from peracarid crustaceans to gastropods, which exhibited different sets of functional traits. Greater eelgrass genetic diversity was strongly correlated with both richness and abundance of peracarids, but less so for gastropods.Main ConclusionsOur results add to a growing body of literature that suggests genetic variation in plant traits influences their associated faunal assemblages via habitat structure. Because peracarids and gastropods exhibited distinct functional traits, our results suggest a tentative indirect link between broad-scale variation in plant genetic diversity and ecosystem function.

The goal of the work is to investigate the role of threespine stickleback Gasterosteus aculeatus in the transfer of substances and energy between the open sea and coastal communities in the White Sea. Five main coastal biotopes habitats in the White Sea were described and their role in spawning of stickleback was evaluated. Almost all sticklebacks (1.9 billion) spawn in the western part of the sea. Approaching the inshore zone to spawn, stickleback brings a significant amount of substance and energy – 6200 tons in fish bodies and 800 tons in eggs. Coastal predators utiliz only 1–2% of this due to their low numbers. The stickleback itself consumes 90–95% of the spawned eggs mainly by destroying nests. Since the stickleback eats mostly its own eggs, it put a low pressure on the coastal prey organisms. The main mortality of stickleback occurs after spawning in the open sea.

The spatial and temporal variability in the dietary preferences of juvenile three-spined stickleback Gasterosteus aculeatus were studied across the typical coastal habitats of Keret Archipelago, Kandalaksha Bay(the White Sea). The sampling of fish using a beach seine was conducted in the late July–early August period and in late August. Additionally, zooplankton samples were collected to conduct a quantitative assessment of the abundance of potential prey items. The similarity percentage (SIMPER) analysis was applied to the data obtained from the stomach content and revealed the five planktonic taxa most prominently contributing to the diet of juvenile sticklebacks. Among these, the copepod Temora longicornis was the most important prey item at marine sites, while Acartia longiremis dominated the diet of fish in the marine lagoon. The calculation of the selectivity index revealed that some taxa (such as A. longiremis) were always avoided by juvenile fish, whereas the selectivity of some taxa increased in late August. In general, juvenile sticklebacks demonstrated a pronounced individual variation in their selectivity, even when a particular prey item was selected positively during the whole period of study. Our data highlight that despite the predominant consumption of easily available prey by juvenile sticklebacks, they demonstrate taxonomic- and size-specific prey selectivity.

While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.

A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5–34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west.

Studies of dietary preferences of migratory species are of great importance as these species connect food webs of habitats across the migration route and thus represent trophic relationships between the spatially disjointed communities. Here we described the dietary preferences of threespine stickleback G. aculeatus in the White Sea during the spawning season using stable isotope and stomach content analyses. The two analyses suggested that during the spawning season, when sticklebacks spend the majority of their time inshore, their diet consists mostly of benthic species, while at the beginning of the spawning season when fish migrating from the offshore were feeding on plankton. Additionally, we demonstrated that stickleback eggs contributed greatly to the diet of both male and female fish. Using Bayesian mixing modeling, we showed that dietary preferences in females were broader than in males, and more variable during the spawning season. While guarding their nests, males fed almost exclusively on eggs. Both stomach contents and isotope signatures demonstrate that by the end of the spawning season sticklebacks again increase the consumption of plankton. Isotope analysis proved to be a more reliable tool to trace this change than stomach content analysis. Our results show that stable isotope and stomach content analyses are complementary in understanding seasonal changes in the dietary composition of stickleback.

Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.

Genetic markers (sex-specific loci of Ga1 and Ga2) have been used to analyze the sex ratio of the threespine stickleback at different stages of ontogenesis. The progeny of all individually tested females includes both males and females, and no significant departures from a 1 : 1 sex ratio has been found in embryos from the natural nests. Juveniles did not demonstrate a sex bias up to one-and-a-half or two months of age, but in older juveniles, females prevailed (this fact has been reported for the first time). Females prevail among spawners, which mostly results from the predominant elimination of males during the spawning and post-spawning periods. The possible causes of this predominance are discussed.

Sexual dimorphism (SD) in the threespine stickleback Gasterosteus aculeatus reflects the different roles of the sexes in reproduction and their adaptations to different ecological niches. We quantified SD in one population of marine stickleback from the White Sea, collected during the spawning period from three spawning grounds, each at a distance of 5 km or less from the others. We used a landmark-based approach to quantify variation in 44 morphometric linear traits. In total, 749 females and 693 males were analyzed. In males, anterior body parts are larger — the base of the caudal fin and armor structures such as the first and second dorsal spines and the pelvic spine. Females have larger posterior bodies — the abdomen, pelvic girdle and the third dorsal spine. The SD of caudal body parts exhibits complex patterns. In White Sea threespine stickleback, SD patterns are generally similar to other populations of the species, but more often show male-biased patterns. Female-biased size SD may be associated with the female biased sex ratio of White Sea stickleback.

Проведена количественная оценка метацеркарий трематод рода Cryptocotyle на поверхности тела у трехиглой колюшки Gasterosteus aculeatus Кандалакшского залива Белого моря. для работы были выбраны три нерестилища, отличающиеся по сочетанию ключевых характеристик среды, влияющих на плотность производителей. отлов рыб проводили трехкратно в течение нерестового периода с 29 мая по 7 июля 2016 г. в начале нереста характеристики заражения у рыб из разных местообитаний были очень сходны, что, скорее всего, указывает на смешивание колюшки во время зимовки. впоследствии во всех биотопах к концу нереста отмечалось увеличение как индекса обилия паразитов (среднее число паразитов на рыбу, включая незараженных особей), так и экстенсивности заражения (доля зараженных рыб). самые высокие значения индекса обилия и экстенсивности заражения наблюдали в лагуне Колюшковая, отличающейся от других нерестилищ колюшки значительной степенью изолированности от моря и замедленным водообменом, способствующими накоплению паразитов у особей. отсутствие у колюшек половых различий по степени заражения указывает на то, что хотя самцы и самки несколько отличаются в отношении пространственного распределения в разные периоды нереста, эти различия недостаточны для того, чтобы привести к различиям в зараженности. отсутствие достоверной связи между индивидуальной зараженностью и размерами тела, вероятно, объясняется высокой вариабельностью размеров рыб разного возраста.

This review summarizes and analyzes data on the threespine stickleback Gasterosteus aculeatus L. of the White Sea, which is currently the most abundant fish in the region and, therefore, plays an important role in inshore and offshore communities. The threespine stickleback was abundant in the 1920s–1940s; its numbers declined significantly between the late 1960s and late 1990s and have increased again since then, showing a positive correlation with water temperature. In order to reveal the mechanisms of changes in the population of this species and to assess its role in the marine ecosystems, various aspects of the population biology of the species (interannual and seasonal population dynamics, spatial heterogeneity, age and sex structure, lipid and fatty acid status, homing, and fluctuating asymmetry), as well as its interactions with other organisms (feeding characteristics of adults and juveniles, role in feeding predatory fish, association with eelgrass, parasite composition and spatial distribution, and relationships with competing species) are analyzed.

A major challenge of contemporary marine science is disentangling consequences of climate change from other impacts, and studying non-target species and using historical resources to see long-term trends can meet this need. However, such data can be fragmented, and here, we demonstrate the potential of leveraging across sources for insight. We assembled a variety of historical sources such as scientific and personal observations, anecdotal information, and archival fisheries data to create an abundance time series on threespine stickleback Gasterosteus aculeatus in the White Sea starting in the late 19th century—the longest time series for this species. Stickleback peaked during the warm period of the 1920–1940s and declined during the colder period of the 1950–1990s and now is the most numerous vertebrate in the sea. Analyses of historical and recent time series based on our own data (2007–2019) showed that stickleback abundance decreases during colder winters. It is not associated with zooplankton biomass, positively correlated with herring Clupea sp. catches and negatively with navaga Eleginus navaga catches. Large population size and food web interactions suggest that change in stickleback abundance has the potential to affect the entire White Sea ecosystem.

In order to assess the accuracy and reliability of age estimates from calcified structures in the three-spined stickleback Gasterosteus aculeatus, we evaluated intra and inter-reader repeatability from three structures: otoliths, gill covers and pelvic spines). Average age estimates were also compared between the structures. The overall intra-reader repeatability of age estimates were highest for otoliths (69%), lowest for gill covers (53%) and intermediate for spine cross-sections (63%). Although four of the seven readers had the highest intra-reader repeatability score for spine cross-sections, the inter-reader variance in this structure was much higher than in others. Otoliths were the easiest in terms of their pre-analysis treatment and exchange of materials (as digital images) between readers. In addition, otoliths are more well-studied compared with the other structures with respect to their development through ontogenesis; hence, age estimates based on otoliths should be the most reliable. Therefore, our recommendation is that whenever possible, analysis of otoliths should be the preferred approach for aging G. aculeatus.

Hypothesis: Fluctuating asymmetry (FA) - random deviations from perfect symmetry that are used as a measure of developmental stability - is an effective indicator of stress and fitness in threespine stickleback. Organisms: The threespine stickleback (Gasterosteus aculeatus) and two other species, the brook stickleback (Culaea inconstans) and ninespine stickleback (Pungitius pungitius), were the focus of a review of the literature. In addition, four populations of G. aculeatus - one anadromous population from the Kamchatka River, two marine populations from the White Sea, and one freshwater population from the White Sea basin - were studied in the field. Methods: A review of the literature relating fluctuating asymmetry to different variables, and a comparison of fluctuating asymmetry in four populations of stickleback, which differed in geographical distribution and life history, using lateral plates and four cranial bones (operculum, lachrymal, third suborbital, quadrate). Results: An appraisal of the literature on fluctuating asymmetry suggests that decreasing interest in FA studies has likely resulted from conflicting research results. To some extent, this problem is likely caused by the morphological structures used in FA analysis, which are generally limited to the lateral plates and pelvic fins. These structures can evolve quickly in response to various environmental changes, thus their fluctuating asymmetry reflects not only individual fitness and stress, but also multiple uncontrolled factors that may directly affect those same structures. Using four cranial bones in our analysis showed lower fluctuating asymmetry in anadromous stickleback from the Kamchatka Peninsula compared with marine and freshwater stickleback from the White Sea and its basin. This may be caused by more favourable feeding conditions in the North Pacific than in the White Sea. The different environmental conditions at these locations did not appear to have a significant effect on fluctuating asymmetry, although the comparison of freshwater, anadromous, and marine populations showed that the fluctuating asymmetry of the structures we used is responsive to these differences. Our FA analysis of the selected bone structures reveals clear heterogeneity in stickleback with different life histories. We suggest that these structures can be considered reliable for studies of fluctuating asymmetry in stickleback fishes.

Hypothesis: Selective sex-related mortality of the marine threespine stickleback in the White Sea causes the female-biased sex ratio observed on the spawning grounds. Organisms: Adult threespine stickleback (Gasterosteus aculeatus) spawning in the inshore zone, and three species of predatory fishes: Atlantic cod (Gadus morhua), shorthorn sculpin (Myoxocephalus scorpius), and fourhorn sculpin (Myoxocephalus quadricornis). Place and times: Kandalaksha Bay, White Sea, Russia; June to August 2012–2018. Methods: The following sampling methods were used: beach seining to determine fish density and local population size, hand collection of dead fish on the spawning grounds, gill netting of predatory fishes, analysis of predatory fish stomach contents to determine the sex of wellpreserved stickleback, and morphological analysis of stickleback spines to determine the sex of decomposed stickleback. Results: The dynamics of stickleback abundance in the lagoon is explained by inshore migration of the fish to the spawning area at the beginning of the spawning period, and their subsequent departure at the end of the spawning season, with females leaving the grounds earlier than males. During spawning (5–30 June), total stickleback mortality reaches about 0.1%; the difference in the relative mortality rates of 0.0044% per day for males and 0.0030% for females is statistically significant. Mortality increases in the post-spawning period, when fish abundance in the inshore zone falls considerably, but remains at a very low level. Because of the low level of non-predation mortality, it cannot be the cause of the female-biased sex ratio observed in the White Sea stickleback population. Predation-associated mortality caused by Atlantic cod and sculpins was male-biased. Based on the stomach contents of predatory fish, the sex ratio of stickleback prey was as follows: cod, 61% males/39% females; sculpins, 82% males/18% females, which was significantly different from the population at sea (35% males/ 65% females). This factor alone, however, is unlikely to explain the prevalence of female stickleback in the lagoon. The eventual offshore male-biased mortality, caused by increased depletion of energy reserves during the spawning period, is probably the main reason for the observed female-biased sex ratio. Correspondence: P.V. Golovin, Saint-Petersburg State University, 16 line V.O. 29, St. Petersburg 199178, Russia. email: pasha-golovin@yandex.ru Consult the copyright statement on the inside front cover for non-commercial copying policies. Evolutionary Ecology Research, 2019, 20: 279–295 © 2019 Pavel V. Golovin

Hypothesis: Marine threespine stickleback manifest homing ability and site fidelity during their spawning period. Organism: The threespine stickleback, Gasterosteus aculeatus. Time and places: June 2015 and June 2016 (during the stickleback spawning period), Koliushkovaya Lagoon, Kandalaksha Bay, the White Sea. Methods: Stickleback were tagged on their inshore spawning grounds about 2 weeks after their inshore migration. We attached plastic tags to their dorsal spines, displaced them 100-300 m away from shore, and recaptured them inshore after periods of one hour to four days. Results: Stickleback caught on their spawning grounds in the lagoon, tagged and displaced a few hundred metres, were able to return to their home site within a day. Males and females exhibited no differences in homing ability. Most fish left their home site within four days of returning, however, indicating that site fidelity is weak. Stickleback caught outside the lagoon in the sea, and tagged and released in the lagoon, spread along the shore in accordance with the density of local fish.

Lake Mogilnoe is a rare example of an anchialine lake (with subterranean connection to the ocean) in the Arctic, a refuge for landlocked populations of marine organisms. The lake has been the subject of intensive studies since the end of the 19th century. Here we demonstrate that between the 2003–07 and 2015–18 observation periods this permanently stratified lake experienced significant changes. The surface salinity increased and exceeded the tolerance limits of many freshwater organisms. The bottom anoxia expanded from one-fifth to one-third of the lake volume. Such a turn in stratification affected both composition and distribution of biota: freshwater zooplanktonic species virtually disappeared, while benthic communities shifted to shallower depths. Although recent changes in the lake stratification are consistent with the long-term trend, their scale is much larger than has been observed during the past 120 years. It was earlier considered that the lake dynamics were mainly affected by human activity in the vicinity of the lake. However, lack of human activity around Mogilnoe during last decades persuades us to search for the natural causes of the recorded changes.

This study uses morphometric analysis for better understanding processes occurring during the spawning period in the population of threespine stickleback Gasterosteus aculeatus. Totally, 270 specimens were sampled in 2016 in the Keret Archipelago (White Sea) from three spawning grounds of different quality in the beginning (28–30 May), middle (15–17 June) and end (7–9 July) of spawning period. Nine characters describing fish body shape were measured on each specimen using scanned image and caliper: 1) Total Length, 2) Standard Length, 3) Head Length, 4) Maxilla Length, 5) Distance Between Head and Pectoral Fin, 6) Body Depth, 7) Body Thickness, 8) Head Thickness, 9) Caudal Length. For analyses, we used ratio of characters 3–9 to Standard Length. Principal Component Analysis has separated several groups of characters, describing the upper part of the body (Characters 3–5), body volume (Characters 6–8), and Caudal Length (9). Separation of the groups was similar in both sexes. All groups of characters showed notable changes during the spawning period. In the beginning, the spatial heterogeneity of samples was low, meaning that in wintering locations the population is not structured. In the middle of spawning season, the highest heterogeneity was observed. Males characterized by larger upper part of the body and larger size, were numerous in high quality spawning grounds (characterized by high density of sea grass and stickleback). This probably results from a competition between territorial males for higher quality spawning grounds. In the end of spawning period no spatial heterogeneity was observed, probably, because most of stickleback left the spawning grounds and no competition for higher quality spawning grounds took place. Spatial heterogeneity was somewhat lower in females, but also statistically significant in several cases. Group of characters describing body volume, in general, showed the decline during the spawning period, reflecting release of eggs in females and loss of energy associated with spawning (more pronounced in males guarding their progeny). Superimposition of several processes, such as competition for fish for better spawning grounds, release of eggs and loss of energy associated with spawning, and inshore and offshore migrations, results in a dynamic and complicated picture of morphological heterogeneity occurring during the spawning season of the threespine stickleback.

Kelps are ecosystem engineers and thus enhance biodiversity and subsidize food webs in nearshore areas. Numerous studies describing diversity and abundance of biota associated with kelp have focused on sub-tropical and temperate waters while kelp forests at high latitudes, where kelp is predicted to expand in distribution, remain mostly unexplored. Kelp forests contribute significantly to regional biodiversity, and associated fauna and the kelp themselves play ecologically important roles as habitat and feeding areas. Here, we report patterns in diversity, abundance and seasonal dynamics of fouling organisms associated with different regions of Saccharina latissima and nearby substrates (including stones of the barren ground). The study was conducted in Kongsfjorden, a high Arctic fjord on the west coast of Spitsbergen; and samples were taken five times between September 2013 and January 2015. Trends in species richness of epifauna were similar for stones and holdfasts: higher in winter (due the presence of rare species), and lower in spring and autumn. Species richness and abundance demonstrated a clear tendency to increase in accordance with substrate stability. Stones housed the most diverse biota compared to living substrates. Holdfasts demonstrated similar patterns in species composition and abundance as stones due their close spatial arrangement and presence of demersal larvae in most of fouling organisms. Similarly, assemblages on blades in prostrate kelp forests are influenced by the species inhabiting stones of the barren ground. Both biotic and abiotic factors, including habitat stability and proximity to source populations, contribute to these spatial and temporal patterns in faunal abundance and diversity.