Harpacticoid Assemblages Research Articles

Environmental stability and long-term variability of harpacticoid copepod assemblages

Harpacticoid copepods of the Chernaya Bay (White Sea) intertidal zone were collected in 45 surveys carried out from spring to autumn over a 25-year period (1996–2020) at three sites that differed in sediment properties. There were no significant long-term trends or seasonal cycles in total abundance. Regarding the species composition, the differences between sites were the most important source of variability over the whole period while the fine-scale (within-habitat) variability was low. Epibenthic species prevailed in fine silty sand, both burrowing and epibenthic species prevailed in medium sand, and interstitial and burrowing species prevailed in coarse sand. A comparison of the data on harpacticoid assemblages from a number of geographically remote loci corroborated the generality of this pattern. In a temporal dimension, the structure of each community was stable until the early 2000s, when the proportion of epibenthic, burrowing and interstitial species changed following changes in sediment properties (increasing siltation at sandy sites and decreasing siltation at the silty site). At each site, there was an increasing long-term trend in diversity (both in total richness and in expected species number). This increase was particularly apparent at sandy sites because of the appearance of epibenthic species. We suggest that sediment composition is the key factor determining the composition of harpacticoid assemblages in space and time. The “ecomorphological profile”, i.e., the proportion of species with different lifestyle and morphological traits, is a useful and informative indicator for describing and typifying these assemblages.

Importance of nonindigenous harpacticoids (Crustacea: Copepoda) decrease with depth in Lake Ontario

Harpacticoid copepods can be a substantial component of the meiobenthic community in lakes and serve an ecological role as detritivores. Here we present the first species-level lake-wide quantitative assessment of the harpacticoid assemblage of Lake Ontario with emphasis on the status of nonindigenous species. Additionally, we provide COI-5P sequences of harpacticoid taxa through Barcode of Life Data System (BOLD). Harpacticoids were collected at depths from 0.1 to 184 m and from a range of substrates from August to September 2018 as part of the Cooperative Science and Monitoring Initiative (CSMI) offshore benthic survey. Twenty-six meiobenthic samples were analyzed using microscopy for community composition analysis of harpacticoids. We found thirteen indigenous and three nonindigenous species of harpacticoid, with the introduced species dominating at shallow depths. The community transitioned from nonindigenous to indigenous species dominance as depth increased. Nonindigenous species accounted for 79% of the community (by abundance) at depths <20 m, 55% from 20 to 40 m, and only 24% at depths >40 m. The nonindigenous species encountered included the first detections of Schizopera borutzkyi (Monchenko, 1967) and Heteropsyllus nunni (Coull, 1975) from Lake Ontario. S. borutzkyi was the most abundant harpacticoid species in the lake, approaching a maximum density of 50,000/m2 and a lake-wide average density of 7,900/m2. Numerically important indigenous species included Bryocamptus nivalis (Willey, 1925), Canthocamptus robertcokeri (Wilson, 1958), Canthocamptus staphylinoides (Pearse, 1905), and Moraria cristata (Chappuis, 1929). The prevalence of nonindigenous harpacticoids in the meiobenthos of Lake Ontario suggests further investigations of Great Lakes meiofauna communities are warranted.

Harpacticoida (Copepoda) from the pelagic zone of the Sea of Okhotsk: diversity, spatiotemporal distribution, and role in benthopelagic coupling

ABSTRACT We analysed the pattern of spatiotemporal distribution of harpacticoid assemblages of 106 plankton samples collected in May–August of 2013–2015 in Prostor Bay, South Kuril Islands (Sea of Okhotsk). Taxonomically and ecologically diverse harpacticoid assemblages were found in the water column. Among the 49 species identified, only one was truly planktonic, while the others were typically benthic, mainly phytal-dwelling forms. The most abundant and rich (42 species) assemblage occupied the shallow (10 m depth) area in the western, stone-bottomed part of the bay with a well-developed phytal zone. In deeper areas, the abundance and diversity of harpacticoids in plankton samples decreased steeply. There was a clear seasonal pattern of abundance, diversity and composition, with a peak in spring and then a decrease. On average, the total abundance was low (64 ind/m2). Neither interannual variations contributed significantly to the harpacticoid distribution. The analysis of the gut contents suggests that the harpacticoids feed on planktonic diatoms in the water column, but their residence time in the water column was short, and their feeding rate was low. In turn, the harpacticoids constituted a permanent but relatively minor fraction of the salmon fry diet. Thus, in quantitative terms, harpacticoids contribute relatively little to benthopelagic coupling in the Prostor Bay ecosystem.

Description of a new species of Nannopus Brady, 1880 (Copepoda: Harpacticoida: Nannopodidae) from Argentinean waters, including an updated key to species.

Both sexes of a new brackish-water species, Nannopus sinusalbi sp. nov. (Nannopodidae) are described from the Baha Blanca estuary (3853S, 6207W) in Buenos Aires Province, Argentina. The only previous record of the genus in the study area was identified as the type species, Nannopus palustris Brady, 1880, with no description or illustrations, hence its authenticity cannot be confirmed. Nannopus brasiliensis Jakobi, 1956 is relegated to species inquirenda in the genus rather than being considered a junior synonym of the type species. Nomenclatural issues related to the usage of the alternative spellings Iliophilus Lilljeborg, 1902 and Ilyophilus sensu Sars (1909) and the unavailability of Ilyophilus canui Kim, Choi Yoon, 2017 are discussed. An updated key to the 18 identifiable species of Nannopus (excluding the type species N. palustris) is presented. The harpacticoid assemblage at the type locality showed a distinct seasonality with N. sinusalbi sp. nov. representing about 8% of the community. The new species showed densities below 5ind.cm‑2 during most of the year, reaching an abrupt peak of 40.17ind.cm‑2 towards the end of the summer, when the maximum proportion of ovigerous females was recorded.

Harpacticoid assemblages (Copepoda: Harpacticoida) in the hyporheic zone of four streams in central Slovenia

Harpacticoids are an important component of meiofaunal assemblages in hyporheic zone. The goal of this study was to investigate distribution patterns of interstitial harpacticoid assemblages from four pre-Alpine streams originating in the Dinaric Karst and flowing into the Ljubljanica River. The sampling was conducted in 2002 at 12 locations distributed at a distance of approximately 1 km along each stream including tributaries, at a depth of 30–60 cm in the wetted channel (three sites per location) and depths from 65 to 160 cm on the stream banks (one site per location) using a Bou-Rouch pump. Concurrently, the interstitial water’s physical and chemical parameters were measured at two sites within each location (streambed, streambank). A total of 24 harpacticoid species were found, 12 of which were stygobionts (i.e., species living exclusively in groundwaters). Among them, two previously unknown species for science were found. Harpacticoid assemblage composition, with the exception of those from the Iška stream, did not differ significantly between the streams, indicating interconnectivity of the interstitial milieu. Sediment structure, amounts of particulate organic matter, conductivity and redox conditions seemed to have certain impacts, indicating the importance of hydrological and geological settings for harpacticoid assemblages.

Habitat-Diversity Relations between Sessile Macrobenthos and Benthic Copepods in the Rocky Shores of a Marine Protected Area

In rocky shore systems, sessile macrobenthic assemblages may act as “ecosystem engineers” for many smaller benthic organisms. Thus, the influence of macrobenthic coverage on the diversity and assemblage structure of the harpacticoid copepod fauna was investigated in the rocky shores of a Marine Protect Area (MPA) in the Ligurian Sea (NW, Mediterranean Sea). Two sampling sites were investigated in two seasons at three different depths on both sub-vertical and inclined reefs. A total of 61 species of copepods mainly represented by Miraciidae, Laophontidae, Longipediidae and Thalestridae were found. The complex micro-topography of these substrata provided a wide variety of niches for many species with different lifestyles that suggests the important role of rocky shores to ensure the functioning of coastal ecosystems. The harpacticoid assemblage structure seemed mainly influenced by season and depth. The temporal spread observed is likely one of the underlying mechanisms of niche segregation that allows many species to co-occur in this specific environment along with a subordinate spatial segregation corresponding to the depth gradient. The results seem to support the hypothesis that the different species composition of the “ecosystem engineer” (and consequently its structure changes) are relevant in structuring the copepod assemblages. The comparison with previous data on general meiofauna underlines that higher surrogacy of the taxonomic identification could be used to study rocky shore communities, but the rich diversity that these systems host can only be understood at the lower taxonomic levels. The same holds for future evaluations of impact of environmental changes (including MPA regulations) on meiofaunal assemblages.

Seasonal variability of meiobenthic assemblages inhabiting the Nottinghambukta tidal flat, SW Spitsbergen

AbstractThe aim of the work was to describe the variability of a group of meiobenthos inhabiting a tidal flat in Nottinghambukta which is influenced by the diverse conditions of a seasonal as well as multi-annual cyclicity. Samples were collected in five series, i.e. during the Arctic spring (2001), summer (2000 and 2001) and autumn (2001). The material for qualitative analysis was collected from sites with different hydrological characteristics. The following major meiobenthic taxa were found: Metazoa, i.e. Nematoda and Crustacea (Ostracoda and Copepoda-Harpacticoida), and Foraminifera. Unstable conditions in the bay result in a seasonal variability in the species composition as well as an uneven colonisation of the Nottinghambukta area by meiobenthos. The lowest taxonomic diversity occurs in summer, but it increases in autumn when the land runoff ceases. Based on the conducted analysis, it can be concluded that the inflow of seawater in autumn brings on the occurrence of new taxa, which probably inhabit the bay temporarily until the summer season during which the highly variable conditions cause a change in the species composition. For the series of samples collected in July 2000 and 2001, the species composition for Harpacticoida was determined. The taxonomic diversity of the harpacticoid assemblage inhabiting the bay was observed in the two subsequent years. Moreover, during the study duration a considerable decrease was observed in the abundance of Ostracoda in Nottinghambukta.

Harpacticoida (Copepoda) in the plankton of Ushuaia and Golondrina Bays, Beagle Channel, Argentina

Harpacticoid copepods form a diverse and abundant group of the meiofauna in marine benthic habitats. Moreover, harpacticoids are frequently found in planktonic samples particularly in shallow and algae-covered coastal waters. Despite their high abundance, little is known about their taxonomy and importance as a component of the food web in the Southern bays of Argentina. Mesozooplankton samples and environmental data were obtained seasonally from Ushuaia and Golondrina Bays (August 2004 to June 2005) and analyzed for the composition and abundance of harpacticoid copepods. Remarkable seasonal changes in the harpacticoid communities were observed. In Ushuaia Bay, nitrogenated nutrients, chlorophyll a, salinity, and temperature were the prevailing environmental parameters that influenced the harpacticoid community, giving rise to different harpacticoid assemblages. The results highlight the importance of the community of Harpacticoida in both bays and provide background data for further studies on zooplankton communities and monitoring programs in marine systems.

Do the presence and physiological stage of algal mats affect the meiobenthic community in a tropical estuary?

The effects of compacted algal mats growing attached to sediments on the abundance and community structure of intertidal sediment meiofauna and harpacticoid copepod assemblages were evaluated on a tropical estuarine mudflat. Differences in fauna based on the presence of algae (within vs. outside the algal patches) and the physiological stages of the algae (live vs. decomposing algal patches) were compared. In general, lower densities occurred within algal patches for most meiofaunal groups, except for harpacticoids, which showed an increase in number in the live algal patches (LAP). Non-metric MDS analysis clearly distinguished both meiofauna community and harpacticoid assemblage in relation to the presence of algae and the physiological stage. Organic matter, carbohydrates, proteins and photosynthetic pigments were higher within algal patches and highly correlated with meiofauna variables. One species of harpacticoid (Cletocamptus sp.1) dominated the LAP samples and thus reduced species richness and diversity of harpacticoids in these samples. The species Robertsonia mourei occurred exclusively in decomposing algal patches (DAP) and probably is an opportunistic species within the DAP samples. Strong differences regarding live and decomposing algae samples highlighted the importance of physiological stage in understanding meiofaunal responses to algal mats.

High resilience of harpacticoid copepods in the landward slope of the Japan Trench against disturbance of the 2011 Tohoku Earthquake

AbstractOn 11 March 2011, an earthquake of magnitude Mw 9.0 known as “the 2011 off the Pacific coast of Tohoku Earthquake” occurred off the coast of Miyagi Prefecture. To assess the effect of the earthquake on the deep‐sea ecosystem, we compared harpacticoid assemblages at six stations (100–6000 m water depth) in the landward slope of the Japan Trench off Sanriku in northeastern Japan. We collected samples at the same locations after 4.5 months (2011) and 1.5 yr (2012) after the earthquake. There were no significant differences in depth‐related patterns of harpacticoid assemblages in terms of diversity and community composition between 2011 and 2012. Changing patterns of harpacticoid community composition along water depth in the Sanriku region after the earthquake did not significantly differ from those in the reference region (Kuril region, 500 km away from the Sanriku region, Japan). Our results suggest that the harpacticoid assemblage at the Sanriku region was not affected by the earthquake or that it quickly recovered after the event. Around our study area, large earthquakes have occurred at 500‐yr intervals on average. The observed high resilience of harpacticoid assemblages against the earthquake suggest that benthos with high resilience against disturbance are dominant under a situation in which large disturbances occur every 500 yr or more.

Littoral Harpacticoida (Crustacea: Copepoda) of Madeira and Porto Santo (Portugal)

The aim of the present investigation is a thorough inventory of the Harpacticoida (Copepoda) of the Portuguese islands Madeira and Porto Santo to provide a basis for comparisons of the harpacticoid faunas of successive elevations of the so called ‘Madeira Hot Spot Track’. Quantitative samples from 10 sampling locations at the coastlines of both islands were analysed (eight from Madeira and two from Porto Santo) and revealed a total of 27 families of Harpacticoida. Nine of the families were determined on species level comprising 43 species of which 31 were new to science. Comparisons of the family and species assemblages at the different Madeiran sampling locations indicate strong habitat heterogeneity as well as differences of the southern from all remaining locations. The sampling locations at the north and east coast are predominately characterized by interstitial taxa, those of the south coast by more robust burrowing or epibenthic taxa. Furthermore the two easternmost sampling locations of Madeira show clear similarity in terms of their harpacticoid assemblages with the sampling locations of Porto Santo. Eighty-eight per cent of the determined species of Porto Santo occur at the coast of Madeira as well (predominately at the easternmost sampling locations) indicating dispersal of Harpacticoida between both islands.

The harpacticoid assemblages (Copepoda: Harpacticoida) in the Western Carpathian spring fens in relation to environmental variables and habitat age

Harpacticoids are an important component of meiofaunal assemblages in springs. No information so far has been available on harpacticoid assemblages of the Western Carpathian spring fens, unique biotopes of high conservation value which cover a very long gradient of mineral content of groundwater, due to the variable geological background setting. Spring fens are isolated habitats of different age which can be assessed by radiocarbon dating of their basal sediment layers. This enables to test a possible effect of habitat age on species composition and species richness. In this study, we examined harpacticoid assemblages in 50 permanent tree-less spring fens (helocrenes) in the Western Carpathians (Slovakia and Czech Republic) in terms of species composition, total abundance, species density, and species richness. We tested mainly the effect of 12 explanatory variables describing water chemistry and temperature, climatic conditions, amount of nutrients, organic carbon, sediment structure, habitat age and size, using Canonical Correspondence Analyses (CCA) with stepwise forward selection. For the computation of species richness rarefaction was used. In total, 20 harpacticoid species were recorded with the total median density of 950 individuals in m −2 . Three significant explanatory variables, Ellenberg Indicator Values of plant community for nutrients, in situ measured pH, and average January temperature, explained together 19.0% (adj. 13.7%) of the total variance in the species composition data. The relationships of harpacticoids to these three explanatory variables were species specific and no uniform response of the total assemblage to the environmental variables was found (in terms of total abundance and number of species). The only exception was the influence of overall unfavourable conditions in the mineral-poor acidic Sphagnum -fens. Pilocamptus pilosus was significantly associated with a higher amount of nutrients and warmer climate. Nutrient enrichment was clearly indicated by a decrease or absence of crenophile Bryocamptus cuspidatus , and accompanied by an increase in ubiquitous Attheyella crassa . Moraria brevipes was confined to low pH, B. cuspidatus showed a high tolerance for low pH, whereas Bryocamptus echinatus preferred alkaline conditions. Despite a significant correlation between habitat age and species density we found no clear evidence that any colonisation driven process could influence the number of harpacticoid species within the tested time scale. We hypothesize that rather other habitat characteristics connected with age, i.e. habitat heterogeneity and stability, may be determinant for species richness. The occurrence of some species (e.g. P. pilosus , B. cuspidatus ) was clearly geographically limited, but due to the spatial structuring of significant environmental variables no conclusion on dispersal limitations could be made.

Trophodynamics of estuarine intertidal harpacticoid copepods based on stable isotope composition and fatty acid profiles

Trophic interactions at the basis of food webs, for instance between meiofauna, primary producers and bacteria, are key drivers of benthic energy fluxes. Yet both qualitative and quantitative information about meiofaunal resource utilization under in situ conditions is scant. By means of natural stable isotope ratios of carbon and nitrogen and of fatty acid (FA) profiles, we examined the variability of in situ resource utilization of a range of harpacticoid copepod species from 5 stations in an estuarine intertidal area. These stations, located in different habitats, differed in sediment granulometry, resource availability, presence/absence of vegetation and other environmental variables, as well as in copepod species composition. Our goal was to describe interspecific differences among harpacticoid species, as well as spatio-temporal variability within species. Despite differences in resource availability between habitats, delta C-13 data clearly point at microphytobenthos (MPB) as the major carbon source to the harpacticoid assemblages at all 5 stations. Small differences in carbon isotopic ratios between co-occurring species indicate some degree of resource differentiation, whereas both the delta N-15 and FA composition suggest that several harpacticoid species obtain MPB carbon indirectly, perhaps through feeding on bacteria or ciliates. For a limited number of species, such as Paraleptastacus spinicauda, clear dietary contributions of suspended particulate matter and bacteria were found, and MPB appeared to have only a small or no contribution. Even in vegetated salt-marsh stations, Spartina anglica detritus did not appear to contribute to copepod diets. The delta C-13 of Cletodidae were highly depleted, reflecting a contribution of methane-derived carbon.

Diversity and environmental control of benthic harpacticoids of an offshore post-dredging pit in coastal waters of Puck Bay, Baltic Sea

Placer extraction in Puck Bay, a shallow (3 m depth) area of the Baltic Sea, resulted in the formation of post-dredging pits. Such dredging activities led to a considerable local disturbance of the soft-bottom communities. Topography and sedimentary characteristics of the disturbed area have been radically changed. It is therefore a matter of concern as to whether these alterations to the environment resulted in any serious permanent changes to the biological communities in the affected areas. Benthic copepod assemblages were examined 10 years after termination of placer digging in one of the post-dredging pits and compared with the fauna in a natural depression (Kuźnicka Hollow) and on the shallow sandy bottom surrounding the pits. Samples were collected on four occasions in 2001–2003. This study has generated ecological information on the status of harpacticoid species inhabiting the dredged and undredged areas in the vicinity. Analyses of data showed that the sampling stations differed significantly, during all the sampling events, in harpacticoid abundance, taxonomic composition and Shannon–Wiener diversity index. The natural depression and the shallow sandy bottom of Puck Bay were found to support specific harpacticoid assemblages. Interstitial and sand-burrowing species (e.g. Paraleptastacus spinicauda) dominate the shallow sandy bottom, and the Kuźnicka Hollow is inhabited mainly by epibenthic and silt-burrowing species (e.g. Halectinosoma curticorne, Tachidius discipes, Microarthridion littorale). The post-dredging pit assemblage showed the presence of epibenthic species, e.g. Tachidius discipes, Dactylopusia euryhalina, and Stenhelia palustris, passively transported into the pit by wave action and currents, possibly with algal mats and/or plant remains. The taxonomic composition and occurrence of harpacticoid species in the post-dredging area is therefore random and accidental.

Bathymetric patterns of α and β diversity of harpacticoid copepods at the genus level around the Ryukyu Trench, and turnover diversity between trenches around Japan

The diversity of harpacticoid copepods was investigated around the Ryukyu Trench (430–7150m), which lies below an oligotrophic subtropical ocean. The α diversity, which is based on the number of genera and Shannon diversity decreased with increasing water depth. The community structure of harpacticoids gradually changed as the water depth increased from the bathyal zone to the hadal zone. Turnover (β) diversity values were equally high between the trench slope, trench floor and abyssal plain. We compared the harpacticoid assemblage obtained from the Ryukyu region with the assemblage from a region around the Kuril Trench (Kitahashi et al., 2013). Turnover diversity values between the two regions (δ diversity) were relatively low at shallow depths, but they increased with increasing water depth and reached their maximum between the trench floors and abyssal plains. These findings indicate that the bathymetric patterns of harpacticoid assemblages differ among regions and that these discrepancies reflect differences in environmental conditions, such as primary productivity level.

Community structure and species diversity of Harpacticoida (Crustacea: Copepoda) at two sites in the deep sea of the Angola Basin (Southeast Atlantic)

The aim of this study was to evaluate compositional differences between harpacticoid (Crustacea, Copepoda) assemblages at two widely separated abyssal locations. During the DIVA 1 cruise of RV METEOR (July/August 2000) to the Angola Basin (Southeast Atlantic), two deep-sea stations, approximately 300 nautical miles apart (Stations 325 and 346), were sampled repeatedly by Multicorer (MUC). For quantitative analyses, 5 MUC samples were selected at random from each of 15 deployments at both stations, totalling 75 cores. Across the study, 7,081 Harpacticoida specimens were encountered and of these 31.4 % were adults and could be analysed to species level: 682 species were identified, with 99.3 % new to science. At northern Station 346, a total of 600 species were recorded—the highest harpacticoid species number ever recorded for a single deep-sea locality. Most species (56 %) were represented by singletons. Multivariate tests identified significant differences between community compositions at the two stations. Diversity, species richness and species density were higher at Station 346, whilst taxonomic distinctness, evenness, and rarefaction were similar between stations. Regression and correlation analyses showed that the difference in species diversity was best explained by species densities rather than species richness. Under-sampling due to low densities was an issue at the southern Station 325. Nevertheless, our study demonstrated significant differences in regional-scale harpacticoid community structures within a single deep-sea basin that would usually be considered a uniform and stable habitat. These observed differences are thought to reflect differences in food availability at the two stations.

Harpacticoid copepod response to epiphyte load variations in Posidonia oceanica (L.) Delile meadows

AbstractWe conducted a field experiment to assess the response of phytal harpacticoids to nutrient‐driven increases of epiphyte load in Posidonia oceanica meadows. First, we evaluated differences in species richness, diversity and assemblage structure of phytal harpacticoids in P. oceanica meadows with differing epiphyte loads. Secondly, we conducted a field experiment where epiphyte load was increased through an in situ addition of nutrients to the water column and evaluated the responses of the harpacticoid assemblages. We predicted that there would be changes in the harpacticoid assemblages as a result of nutrient‐driven increases of epiphyte load, and that these changes would be of a larger magnitude in meadows of low epiphyte load. Our results show that the harpacticoid fauna (&gt;500 μm) present in P. oceanica meadows in the Bay of Palma comprised taxa which are considered phytal and other less abundant ones previously described as sediment dwellers or commensal on other invertebrate species. Nutrient addition had an overall significant effect on epiphyte biomass and on harpacticoid abundance, diversity and assemblage structure, possibly as a response to the increased resources and habitat complexity provided by epiphytes. The abundance of dominant species at each location was favoured by nutrient addition and in some cases correlated with epiphytic biomass, although never strongly. This may indicate that structural complexity or diversity of the epiphytic cover might be more important than the actual epiphytic biomass for the harpacticoid species investigated. More species‐specific studies are necessary to ascertain this and clarify the relationships between harpacticoids and epiphytes in seagrass meadows. To our knowledge, this is the first account of harpacticoid species associated with P. oceanica leaves and the epiphytic community they harbour in the Mediterranean Sea.

Assemblages gradually change from bathyal to hadal depth: A case study on harpacticoid copepods around the Kuril Trench (north-west Pacific Ocean)

We investigated the genus diversity and community composition of harpacticoid copepods and their relationship with environmental factors around the Kuril Trench (490–7090m). Harpacticoid densities did not decrease with water depth and were highest at 1000m water depth. Diversity values based on the number of genera, Shannon diversity and the expected number of genera (rarefaction) indicated unimodal patterns with water depth, with peaks at intermediate depth; genus evenness increased with water depth and slightly decreased at hadal depths. This result suggested that the general relationship between water depth and diversity described for macrofauna and megafauna could be extended to meiofauna across all depth ranges. However, the regulating factor that affects harpacticoid diversity could not be identified. The community composition of harpacticoids gradually changed with water depth (from bathyal to hadal depths). In addition, comparison of assemblages between the trench slope, trench floor and abyssal plain suggested that the community found at hadal depth was largely different from those found on the trench slope and abyssal plain. Multivariate analyses suggested that water depth, or certain factors associated with water depth, affects harpacticoid assemblages around the Kuril Trench.

Assemblages of Harpacticoida (Crustacea: Copepoda) from the Ryukyu and Kuril Trenches, north-west Pacific Ocean

To examine the specific features of trench communities, spatial changes in the assemblages of harpacticoids were investigated at the family level around the Ryukyu Trench (the Ryukyu region) and Kuril Trench (the Kuril region). In the Ryukyu region, there were high average dissimilarities in the harpacticoid assemblages among the trench, trench slope and abyssal plain, indicating that the assemblage structures differ substantially between these topographic settings at the family level. Conversely, in the Kuril region, the average dissimilarities in harpacticoid assemblages between the trench and the trench slope and between the trench and the abyssal plain were lower than that between the slope and the abyssal plain. This result suggests that the hadal assemblage is a transition zone between the slope and the abyssal plain in this region. In addition, the analyses indicate that the composition of harpacticoid assemblages is influenced by the quantity of organic matter in the Ryukyu region, while sediment properties play a key role in the Kuril region. Comparisons of the assemblages between the two regions, however, revealed that the average dissimilarities between the trenches and between the abyssal plains were higher than that between the adjacent slopes. This result suggests that interchange among regions is difficult for deep-sea benthic animals, including harpacticoid copepods, likely due to the presence of physical barriers around trenches.

Trampling on coral reefs: tourism effects on harpacticoid copepods

Human trampling is a common type of disturbance associated with outdoor recreational activities in coastal ecosystems. In this study, the effect of trampling on the meiofaunal harpacticoid copepod assemblage inhabiting turfs on a coral reef was investigated. In Porto de Galinhas, northeastern Brazil, reef formations near the beach are one of the main touristic destinations in the country. To assess trampling impact, two areas were compared: a protected area and an area subject to intensive tourism. Densities of total Harpacticoida and of the most abundant harpacticoid species showed strong reductions in the trampled area. An analysis of covariance revealed that the loss of phytal habitat was not the main source of density reductions, showing that trampling affected the animals directly. In addition, multivariate analysis demonstrated differences in the structure of harpacticoid assemblages between areas. Of the 43 species identified, 12 were detected by the Indicator Species Analyses as being indicators of the protected or trampled areas. Moreover, species richness was reduced in the area open to tourism. At least 25 harpacticoids are new species for science, of these, 20 were more abundant or occurred only in the protected area, while five were more abundant or occurred only in the trampled area; thus, our results highlight the possibility of local extinction of still-unknown species as one of the potential consequences of trampling on coral reefs.