Composition Of Assemblages Research Articles

Rainfall and soil properties driver the temporal dynamics of arbuscular mycorrhizal fungal assemblages in a seasonally dry tropical forest

The Seasonally Dry Tropical Forests (SDTF), distributed from Mexico to northern Argentina, are habitat to a unique biodiversity. Among these forests, the Caatinga stands out, occupying a large part of the Brazilian Northeast and is subject to cycles of anthropic disturbance and abandonment of exploited areas. Understanding how microbial communities respond to environmental changes is crucial, especially considering the various ecosystem services provided by microorganisms. Among soil microorganisms, arbuscular mycorrhizal fungi (AMF) play a significant role in the maintenance of terrestrial ecosystems. In this study, we aimed to evaluate the structure, composition, and distribution of AMF assemblages, as well as their main drivers, in regeneration areas of the Caatinga. Soil samples were collected in the Catimbau National Park (Pernambuco State), including an old-growth forest representing undisturbed areas, and in early, intermediate, and late regeneration areas. The composition of AMF assemblages differed among regenerating areas and old-growth forest, but their distribution is not related and conditioned to plant assemblages. Instead, soil properties and rainfall are the main factors structuring these assemblages in SDTF. A total of 83 taxa of AMF were identified. Glomus and Acaulospora, which exhibit respectively ruderal and stress-tolerant life strategies were the most abundant genera. The highest number of unique AMF species was recorded in the old-growth forest, contrasting with the late regeneration areas which had the lowest number. The results showed that deterministic processes (soil and rainfall) are structuring the AMF assemblages in areas under regeneration process in SDTF. Plants and AMF do not recover simultaneously over the evaluated regeneration times.

Variations in the Odonata Assemblages: How Do the Dry Season and Water Bodies Influence Them?

Diverse abiotic and biotic factors drive the ecological variation of communities across spatial and temporal dimensions. Within the Amazonian landscape, various freshwater environments exhibit distinct physicochemical characteristics. Thus, our study delved into the fluctuations of Odonata assemblages amidst distinct water bodies within Amazonia, encompassing two distinct climatic seasons. Comparative analysis was conducted on Odonata species diversity and assemblage composition across a blackwater pond, a lake, and a stream, spanning the initiation and culmination of the dry season in the southwestern Amazon region in Peru. Our methodology involved capturing adult Odonata using entomological nets on three separate occasions between 11:00 and 14:00h for each water body in May (beginning of the dry season) and October (end of the dry season) of 2018. We also evaluated the influence of temperature, precipitation, and percent cloud cover on the abundance and richness of adult Odonata. Species richness and composition differed among the three water bodies in both periods of the dry season. No effect of the dry season periods on species richness and abundance was observed. However, except in the oxbow lake, the more abundant species were substituted to the end of the dry season. Our study highlights the influence of water body types on Odonata species diversity and composition. The effects of the sampling period during the dry season may not be immediately apparent in conventional diversity metrics, such as species richness and abundance. Instead, its effects manifest predominantly in the relative abundance of the species that compose these assemblages.

Predation effects on benthic communities are maximized by greater taxonomic richness and diversity in Subtropical SW Atlantic

Predation effects on benthic communities are locally influenced by biological and ecological processes, such as recruitment, competition, and habitat features. We studied three Southwestern Atlantic (SWA) subtropical reef habitats (a rhodolith bed, a coral reef, and a rocky shore) to test if the predation effects on benthic communities overwhelm the habitat-context differences. We deployed panels protected and unprotected from predators on the three habitats, retrieved the panels after 45 days and quantified the recruitment of benthic sessile organisms. Despite differences in the composition of benthic assemblages, the effect of predation was mainly driven by the reduction of the ubiquitous polychaeta Spirorbidae in the three habitats. For the rhodolith bed, which supported a higher taxonomic richness and diversity than the other habitats, predation effects were higher and also driven by the reduction of other taxa. Although we recorded a greater predation effect in more diverse reefs, we attribute this result to small scale traits intrinsic to each habitat instead large-scale oceanographic patterns. Our results add pieces into the debate about how predation affects marine habitats and the importance of small-scale understanding for direct management actions in marine conservation.

Lipid transfers within the lower food web of western Arctic seas

Polar marine ecosystems are undergoing major transformations due to climate change. Alterations of the physical and chemical growth conditions for plankton are likely to propagate through the food web, potentially having major consequences for the animals that Inuit harvest for subsistence. These alterations can impact the nutritional qualities of plankton through physiological responses or indirectly via changes in the taxonomic composition of assemblages. This study focuses on lipids, which provide a vital source of energy in cold waters, and on essential fatty acids (EFA), such as omega-3 and omega-6 FA, which are necessary for the function, growth, and reproduction of organisms. To better understand how EFA propagate and accumulate in the lower food web, we compared the fatty acid composition of phytoplankton and copepods across a large portion of the western Arctic. The bulk lipid profiles of copepod assemblages were determined largely by their taxonomic composition, but specific fatty acid groups (e.g., omega-6 and saturated fatty acids) exhibited strong correlations with water properties (e.g., pH, salinity). A comparative analysis of specific fatty acids suggests that the animals accumulate eicosapentaenoic acid (EPA) but metabolize its precursors, although these processes were not measured directly. The proportions of EPA, docosahexaenoic acid, and specific omega-7 FA (e.g., 16:1ω7) were much higher in copepods than in phytoplankton, and a fatty acid diatom marker accounted for over 45% of the fatty acid pool in copepods. The positive relationship between proportions of this marker in copepods and phytoplankton implies that the fatty acid content of copepods is influenced primarily by recent feeding. These results underscore the importance of long-lived subsurface chlorophyll maxima for trophic transfers of EFA in the strongly stratified waters of the Pacific-influenced sector of the Arctic Ocean and question the paradigm that copepods rely principally on brief surface blooms to rapidly store lipids for the following winter.

Shifts in dominance of benthic communities along a gradient of water temperature and turbidity in tropical coastal ecosystems.

Tropical coastal benthic communities will change in species composition and relative dominance due to global (e.g., increasing water temperature) and local (e.g., increasing terrestrial influence due to land-based activity) stressors. This study aimed to gain insight into possible trajectories of coastal benthic assemblages in Raja Ampat, Indonesia, by studying coral reefs at varying distances from human activities and marine lakes with high turbidity in three temperature categories (<31°C, 31-32°C, and >32°C). The benthic community diversity and relative coverage of major benthic groups were quantified via replicate photo transects. The composition of benthic assemblages varied significantly among the reef and marine lake habitats. The marine lakes <31°C contained hard coral, crustose coralline algae (CCA), and turf algae with coverages similar to those found in the coral reefs (17.4-18.8% hard coral, 3.5-26.3% CCA, and 15-15.5% turf algae, respectively), while the higher temperature marine lakes (31-32°C and >32°C) did not harbor hard coral or CCA. Benthic composition in the reefs was significantly influenced by geographic distance among sites but not by human activity or depth. Benthic composition in the marine lakes appeared to be structured by temperature, salinity, and degree of connection to the adjacent sea. Our results suggest that beyond a certain temperature (>31°C), benthic communities shift away from coral dominance, but new outcomes of assemblages can be highly distinct, with a possible varied dominance of macroalgae, benthic cyanobacterial mats, or filter feeders such as bivalves and tubeworms. This study illustrates the possible use of marine lake model systems to gain insight into shifts in the benthic community structure of tropical coastal ecosystems if hard corals are no longer dominant.

Do different camera trap lures result in different detection rates of vertebrates because of their attractiveness to invertebrates?

SummaryThe type of attractant used in camera trap lures is recognised as an important methodological decision. We investigated whether the type of attractant in lures indirectly influences detectability of wildlife on cameras via differential attraction of invertebrates which themselves constitute prey of insectivorous animals. We indexed invertebrate abundance using pitfall and sticky‐traps at 36 camera stations deployed in a Latin Squares design for 5 days, with three lure options (peanut‐butter, tuna oil and control) in a coastal mosaic, at Cape Otway, Victoria, Australia. We classified vegetation types (habitat) as: low (no or sparse), medium (grass), and high (shrubs) from aerial imagery and estimated their percentage cover at each grid point (medium and high were uncorrelated and included as separate variables in models). We first examine if attractant types or the habitat influence invertebrate abundance and assemblage, and then examine whether invertebrate abundance influences vertebrate detectability on cameras. There was a trend for the composition of terrestrial invertebrate assemblages to be influenced by lure type (peanut‐butter, tuna oil and control attractants) and the proportional cover of medium height vegetation within 20 m; however, assemblage composition was clearly influenced by the proportional area of high vegetation cover within 20 m. The detection probability of insectivorous birds increased where medium‐sized (2.5–5 mm) flying invertebrates were present whereas insectivorous mammal detectability increased with terrestrial invertebrate species richness. Mammal detections are more likely associated with use of habitats that have more diverse invertebrate communities. This study provides some support to the hypothesis of the indirect mechanism whereby bird detections are influenced by invertebrate attraction to lures. Therefore, lure choice for camera traps is critical and the possibility of guild‐level biases in detection suggests that cautious interpretation of results is required.

Effects of a beaver dam on the benthic copepod assemblage of a Mediterranean river

As known “ecosystem engineers”, beavers influence river hydrology, geomorphology, biochemistry, and biological assemblages. However, there is a lack of research regarding the effects of beaver activities on freshwater meiofauna. In this study, we investigated the taxonomic and functional composition of the benthic copepod assemblage of a segment of the Tiber River (Italy) where a beaver dam, created about 7 weeks before our survey, had formed a semi-lentic habitat upstream and a lotic habitat downstream of the dam. We also analyzed the copepod assemblage before and after a flood event that destroyed the beaver dam, providing a unique opportunity to observe changes in a naturally reversing scenario. Our analyses revealed that, while the taxonomic composition and functional traits of the copepod assemblage remained largely unchanged across the recently formed semi-lentic and lotic habitats, substantial differences were evident between the dammed and undammed states. The dammed state showed lower copepod abundances, biomass, and functionality than the undammed one. These results highlight the role of beaver dams in changing the composition and functionality of meiofaunal assemblages offering insights into the dynamic interactions within aquatic ecosystems.

A Comparison of Methods of Visual Census and Cryptobenthic Fish Collecting, an Integrative Approach to the Qualitative and Quantitative Composition of the Mediterranean Temperate Reef Fish Assemblages

The present research quantitatively compared the fish composition among two methods for non-cryptic benthic fish species and one method for cryptobenthic fish species for the first time for the Mediterranean temperate reef fish assemblage. A visual census of fishes was performed within a cylinder of 4 m radius and within a cylinder of 2 m radius, while the cryptobenthic fishes were collected using a square of 1 m2 with anesthetic. The data and material were collected at fifty sampling points. The visual census methods together recorded 31 species, and the square with anesthetic method recorded 18 species. The quantitative comparison of methods of visual census and cryptobenthic fish collecting showed significantly different species richness, total fish abundance, and fish assemblage structure among methods. The applied methods were highly complementary. The cylinder of 2 m radius is well suited for epibenthic fishes and the cylinder of 4 m radius is reliable for hyperbenthic and benthopelagic fishes. Therefore, each of the methods well covered one of three components of ichthyobenthos (hyperbenthic, epibenthic, and cryptobenthic fishes), and all three methods together provided a far more complete assessment of fish species composition than any individual census method for the Mediterranean littoral benthic fishes.

ForCenS-LGM: a dataset of planktonic foraminifera species assemblage composition for the Last Glacial Maximum

Species assemblage composition of marine microfossils offers the possibility to investigate ecological and climatological change on time scales inaccessible using conventional observations. Planktonic foraminifera - calcareous zooplankton - have an excellent fossil record and are used extensively in palaeoecology and palaeoceanography. During the Last Glacial Maximum (LGM; 19,000 – 23,000 years ago), the climate was in a radically different state. This period is therefore a key target to investigate climate and biodiversity under different conditions than today. Studying LGM climate and ecosystems indeed has a long history, yet the most recent global synthesis of planktonic foraminifera assemblage composition is now nearly two decades old. Here we present the ForCenS-LGM dataset with 2,365 species assemblage samples collected using standardised methods and with harmonised taxonomy. The data originate from marine sediments from 664 sites and present a more than 50% increase in coverage compared to previous work. The taxonomy is compatible with the most recent global core top dataset, enabling direct investigation of temporal changes in foraminifera biogeography and facilitating seawater temperature reconstructions.

Succession and seasonality drive tropical butterfly assembly after an extreme hurricane

AbstractThe composition and biodiversity of insect community assemblages are mediated by a complex set of biotic and abiotic factors. Among these factors are forest structure and atmospheric variables (like temperature and humidity), which are heavily influenced by frequent hurricane activity in the Caribbean. Despite this, changes in Caribbean insect assemblages as forests recover from hurricane disturbance are poorly documented. Butterflies represent a charismatic model taxon in biodiversity and conservation, and are thus an ideal subject for exemplifying these shifts in insect abundances and diversity across ecological succession. Here, we monitored butterfly communities in two Puerto Rican forests differing in structure (i.e., canopy height, tree size) to assess butterfly diversity, abundances, and community level wing traits (size and color) over 1 year, beginning 6 months after Hurricane Maria. Monthly sampling over the course of 1 year revealed no relationships between abundances and canopy openness or humidity; instead, species abundances fluctuated seasonally and were nonlinearly correlated with temperature. In contrast, wing size and color were linearly correlated with abiotic variables. Specifically, wings were larger in cooler and more open conditions. Wing color saturation and brightness were negatively correlated with humidity. Our results suggest that, first, a functional approach may provide better insight into the factors mediating species responses to disturbances. Second, further disentangling abundance seasonality from impacts of extreme disturbances necessitates long‐term monitoring.Abstract in Spanish is available with online material.

Mesopelagic fish assemblages in the Mauritanian Upwelling System off Northwest Africa with oxygen as a major driving force

The aims of this study were to determine the community composition and environmental drivers of mesopelagic fishes in the Mauritanian Upwelling System. Mesopelagic fish communities were sampled at 17 stations in August of 2016 off the coast of Senegal and Mauritania using a non-closing rectangular midwater trawl (RMT). This subregion is the most productive area of the Canary Current and has a pronounced and permanent oxygen minimum zone (OMZ). The sampling area was mainly composed of low-oxygenated South Atlantic Central Water, except for 1 station, where North Atlantic Central Water prevailed. Three distinct mesopelagic fish communities were identified. One community occurred in the vicinity of a coldwater eddy and was dominated by the myctophid Benthosema glaciale. In contrast, the gonostomatid genus Cyclothone prevailed in the other 2 communities and made up 62 and 51% of the total fish abundance. Our analyses revealed that the environmental factors that primarily influenced the composition of these mesopelagic fish assemblages were the oxygen concentrations at 10, 100, and 600 m depth. The present study shows that the mixing of water masses at frontal zones leads to communities representative of both water masses. In the case of the Mauritanian upwelling region, a high portion of the mesopelagic fish species were well adapted to OMZ conditions.

Seasonal Changes of Surface-Active Beach Invertebrate Assemblages in Southern Central Victoria, Australia

Invertebrates play a critical role in beach ecosystems, and seasonal variation in their occurrence and abundance likely influences food webs. We examine and characterise seasonal patterns in invertebrate activity on a temperate, southern sandy dune and beach ecosystem at Venus Bay, Victoria, Australia. We index invertebrate abundance, diversity and assemblage composition at fixed-site pitfall traps which were deployed in four transects from the lower dunes to the beach. Seasonal differences occurred in assemblage composition (foredunes only), richness and abundance. Insects dominated assemblages in summer, spring and autumn; crustaceans dominated winter assemblages. Morphospecies richness was lowest in winter (139% higher in summer and 169% higher in autumn). Our results contrast with other studies from temperate beaches in that (1) richness was higher on beaches compared to in foredunes across all seasons and (2) abundance differed significantly such that winter abundance was higher than for all other seasons. Possible explanations include the exposed nature of the study foredunes, marine ecological subsides in the form of beach wrack in winter and/or between-site variations in such factors. Further studies would usefully examine between-beach variation in seasonality in invertebrate activity in foredunes and dunes.

Effects of plant leaf traits, abundance and phylogeny on differentiation of herbivorous insect assemblages in Mediterranean mixed forest

AbstractHerbivorous insect assemblages are functionally diverse, with each species exploiting plant tissues in different ways. Availability and palatability of plant tissues influence the diversity and composition of herbivorous insect assemblages. However, few studies have compared herbivorous insect assemblages and their ecological correlates across multiple plant species within the same plant community. Here, we sampled insect assemblages from the canopies of 1060 plants belonging to 36 woody species in two mixed Mediterranean forest stands. 401 insect species were classified as herbivores and grouped into sucker or chewer guilds. We explored differences in the diversity and composition of each insect guild across plant species, and tested their relationships with plant leaf traits, abundance or phylogeny, and explored whether the structures of plant-herbivorous insect networks depended on any of the studied plant traits. Plant identity accounted for the highest proportion of variation in the composition of each insect guild. Plant species abundance showed a positive effect on both insect guilds’ diversity. Suckers’ diversity was higher in plant species with deciduous leaves and low SLA, while the composition was more similar between phylogenetically closer plant species. Chewers diversity increased with the leaf area, while plants with similar LA, leaf nitrogen, SLA and distinct leaf habit showed more similar assemblages. Similarly, closely related angiosperms showed similar chewer assemblages. Plant–insect interaction networks present a modular structure, in which plants belonging to the same module tend to be related and share more sucker species. We add to the evidence supporting the role of plant species features as filters for structuring their associated herbivore insect assemblages.

The stability of bird assemblages across time and the reliability of snapshot surveys

Abstract‘Snapshot’ surveys conducted over 1 year or less are widely used to describe avian community composition. Maron et al. (Austral Ecology, 2005, 30, 383) questioned the utility of snapshot surveys and the conclusions drawn from them following repeat bird surveys at 26 sites in western Victoria, 7 years after initial surveys. They concluded, ‘the distribution of most species did not differ significantly from that expected if species had redistributed at random among sites’. Only five of 54 species recorded in both years had distributions that changed significantly less than expected among sites between the survey periods. We question whether this is the exception rather than the rule for Australian landbird communities in wooded habitats for three reasons: (1) passerine species dominate these communities and tend to remain faithful to a site once a breeding territory has been established; (2) most landbird species are sedentary or migratory, not nomadic; and (3) most Australian passerines are long‐lived, so surveys conducted within decadal timeframes may sample the same individuals. We examined the constancy of bird community composition by conducting repeat surveys at 29 sites in two vegetation types in the Namoi Valley, northern New South Wales, 7 years after the first survey. Bird assemblage composition in our study exhibited high levels of turnover between surveys, but 21 of 62 species present in both survey periods were significantly more likely to be found at the same sites in the second period as the first, and the tendency of most species was of site fidelity. Mantel tests demonstrated that assemblage composition at the same sites was more similar than expected by chance. Moderate levels of site fidelity among species and significant levels of assemblage composition constancy among sites should be the expectation when monitoring Australian landbird communities in wooded habitats over extended timeframes, except in the cases of major landscape transformation and extreme climatic disruptions.

Scale-dependent influences of environmental, historical, and spatial processes on taxonomic and functional beta diversity of Japanese bat assemblages.

This study investigated the relative influences of environmental, spatial, and historical factors, including the island-specific history of land connectivity, on bat assemblages in the Japanese Archipelago. We collected bat distribution data from 1408 studies and assigned them to Japan's First Standard Grid (approximately 6400 km2). Japanese bat assemblages were analyzed at two scales: the entire Japanese Archipelago comprised 16 islands and exclusively the four main islands. At first, we calculated taxonomic and functional total beta diversity (β total) by Jaccard pairwise dissimilarity and then divided this into turnover (β repl) and richness-difference (β rich) components. We conducted hierarchical clustering of taxonomic beta diversity to examine the influence of the two representative sea straits, Tsugaru and Tokara, which are considered biogeographical borders. Variation partitioning was conducted to evaluate the relative effects of the three factors on the beta diversity. Clustering revealed that the Tokara Strait bordered the two major clades; however, the Tsugaru Strait did not act as a biogeographical border for bats. In the variation partitioning, shared fraction between spatial and historical factors significantly explained taxonomic and functional β total and taxonomic β repl at the entire archipelago scale, but not at the four main islands scale extending only Tsugaru Strait but not Tokara Strait. Pure environmental factors significantly explained functional β total at both scales and taxonomic β total only at the four main islands scale. These results suggest that spatial and historical factors are more pronounced in biogeographical borders, primarily structuring assemblage composition at the entire archipelago scale, especially in taxonomic dimension. However, current environmental factors primarily shape the assemblage composition of Japanese bats at the main island scale. The difference in results between the two scales highlights that the primary processes governing assemblages of both dimensions depend on the quality of the dispersal barriers between terrestrial and aquatic barriers for bats.

Climate warming shifts riverine macroinvertebrate communities to be more sensitive to chemical pollutants.

Freshwaters are highly threatened ecosystems that are vulnerable to chemical pollution and climate change. Freshwater taxa vary in their sensitivity to chemicals and changes in species composition can potentially affect the sensitivity of assemblages to chemical exposure. Here we explore the potential consequences of future climate change on the composition and sensitivity of freshwater macroinvertebrate assemblages to chemical stressors using the UK as a case study. Macroinvertebrate assemblages under end of century (2080-2100) and baseline (1980-2000) climate conditions were predicted for 608 UK sites for four climate scenarios corresponding to mean temperature changes of 1.28 to 3.78°C. Freshwater macroinvertebrate toxicity data were collated for 19 chemicals and the hierarchical species sensitivity distribution model was used to predict the sensitivity of untested taxa using relatedness within a Bayesian approach. All four future climate scenarios shifted assemblage compositions, increasing the prevalence of Mollusca, Crustacea and Oligochaeta species, and the insect taxa of Odonata, Chironomidae, and Baetidae species. Contrastingly, decreases were projected for Plecoptera, Ephemeroptera (except for Baetidae) and Coleoptera species. Shifts in taxonomic composition were associated with changes in the percentage of species at risk from chemical exposure. For the 3.78°C climate scenario, 76% of all assemblages became more sensitive to chemicals and for 18 of the 19 chemicals, the percentage of species at risk increased. Climate warming-induced increases in sensitivity were greatest for assemblages exposed to metals and were dependent on baseline assemblage composition, which varied spatially. Climate warming is predicted to result in changes in the use, environmental exposure and toxicity of chemicals. Here we show that, even in the absence of these climate-chemical interactions, shifts in species composition due to climate warming will increase chemical risk and that the impact of chemical pollution on freshwater macroinvertebrate biodiversity may double or quadruple by the end of the 21st century.

Comparative foraging behavior of 3 heron species in small standing-water ecosystems in the arid zone of Oman

Abstract The composition of assemblages, diet and behavior of waterbird species with similar ecological features are important aspects in the functioning of aquatic ecosystems. Closely related animal species often share resources such as space and food in ways that reduce competition, but if the diets of different species strongly overlap, interspecific competition may intensify. This analysis examined behavioral data relating to Great Egret, Little Egret, and Squacco Heron to explore their foraging efficiencies in rich aquatic habitats in an arid zone during post-breeding movements. The fieldwork was carried out in small estuaries of a Wadi on the southern coast of Oman. The frequency of interactions was the highest in Squacco Heron and the lowest in Great Egret. However, the differences in the numbers of inter- and intra-specific interactions between the 3 species were significant. Activity indices calculated for a 5-min period, i.e., the number of interactions (interaction index) and times of flying and walking (movement index) differed among the 3 species. The number of successful attacks was the highest in Squacco Heron, while the foraging effectiveness of Great Egret and Little Egret was similar. GLM analysis showed that only the movement index was significant, as it had a positive impact on individual foraging success. Great Egret caught more fish than the other 2 heron species which, in turn, caught a greater number of smaller prey items, mostly invertebrates. This study shows that heron species in the same rich habitat employ different foraging tactics. In comparison to the other two heron species, the foraging tactics of Squacco Heron seem to be the most susceptible to competition. However, its greater mobility and using different foraging tactics, enhance its foraging success.

Kelp holdfasts in the Great African Seaforest provide habitat for diverse assemblages of macroinvertebrates

Kelp forests along the southwestern and west coasts of South Africa, dominated by the species Ecklonia maxima and Laminaria pallida, are locally termed ‘the Great African Seaforest’. They form 3-dimensional biogenic habitats that provide 4 distinct microhabitats—canopy, fronds, stipe and holdfast—with the latter typically supporting the highest abundance and diversity of associated macroinvertebrates. The macrofauna inhabiting kelp holdfasts in South Africa have rarely been studied, resulting in a near complete lack of baseline data. In this study, macrobenthic assemblages from 40 E. maxima holdfasts were examined over 2 marine ecoregions and 4 locations. Macroinvertebrates were identified and counted for univariate and multivariate analyses using family-level data. A total of 120 families from 9 phyla were identified and were generally dominated by Arthropoda (48 families), Annelida (24 families) and Mollusca (23 families). Marine ecoregion had no significant effect on composition of macroinvertebrate assemblages, whereas location had a significant effect. There was no significant relationship between holdfast volume and macroinvertebrate diversity or abundance, suggesting that other environmental and physicochemical factors are important in determining community structure. This study serves as a baseline for future research aimed at understudied holdfast macroinvertebrate communities in the Great African Seaforest.

Metamorphic evolution of sillimanite gneiss in the high-pressure terrane of the Western Gneiss Region (Norway)

Abstract. Sillimanite-bearing gneisses in the Romsdal region of the Western Gneiss Region (south Norway) have been investigated to document the presence, formation, composition and petrological evolution of the sillimanite-bearing assemblages. Sillimanite is found in augen gneiss, as nodular gneiss, and in well-foliated sillimanite–mica gneiss. Lenses and layers of eclogite occur within the gneiss units. The sillimanite-bearing gneisses are heterogranular and dominated by quartz, plagioclase (An29–41), K-feldspar and biotite (Mg# = 0.48–0.58; Ti = 0.16–0.36 a.p.f.u.), with variable amounts of white mica (Si = 6.1–6.3). K-feldspar occurs as porphyroclasts in augen gneiss, and garnet constitutes resorbed porphyroblasts. Garnet (Alm46–56Sps24–36Prp10−20Grs4–6; Mg# = 0.22–0.29) shows rimward-decreasing Mg#, together with a smaller grossular decrease and a marked spessartine increase up to Sps36. The foliation is defined by crystal-preferred-orientation micas, elongation of shape-preferred-orientation coarse K-feldspar phenocrysts and a modal banding of phases. Sillimanite occurs as coarse orientation-parallel matrix porphyroblasts, as finer grains and as fibrolitic aggregates. Quartz constitutes coarser elongated grains and monomineralic rods. Pseudosection modelling suggests that the peak-metamorphic mineral assemblage of garnet–sillimanite–feldspar–biotite–quartz–ilmenite–liquid equilibrated at temperatures up to 750 °C and pressures of 0.6 GPa. Subsequent retrogression consumed garnet. Mineral replacement and melt crystallization involved sillimanite, white mica, K-feldspar and quartz. The results document a metamorphic retrogression of the sillimanite gneisses in accordance with the presence of remnants of eclogites and high-pressure granulites in this northwestern part of the Western Gneiss Region.

Different approaches to estimate benthic metazoan diversity associated with free-living macroalgae (Fucus vesiculosus) on shallow soft sediments

Habitat complexity can boost biodiversity by providing a wide range of niches allowing species co-existence. Baltic Sea benthic communities are characterised by low species diversity. Thus the occurrence of the habitat forming macroalga Fucus vesiculosus may influence benthic communities and promote diversity. Here biodiversity estimates were obtained through conventional and eDNA approaches for the benthic assemblages associated with free-living Fucus and the adjacent bare-sediment habitats at six sites from the Northern Baltic Proper and the Gulf of Finland. Free-living F. vesiculosus habitats are heterogeneous with biodiversity estimates varying considerably among sites. The additional habitat complexity provided by F. vesiculosus tended to improve taxa richness as a result of additional epifauna assemblages, although macroinfaunal taxa richness and abundance was often reduced. Consequently the complex habitats provided by free-living F. vesiculosus often improve biodiversity, yet alters the composition of assemblages in soft sediment habitats and consequential ecosystem functioning. The study emphasised the disparity in biodiversity estimates achieved when employing different biodiversity approaches. Biodiversity estimates were more similar within approaches compared to between habitat types, with each approach detecting exclusive taxa. Consequently, biodiversity estimates can benefit from a multi-approach design where both conventional and eDNA approaches are employed in complement.