Horizontal and vertical distribution of meiofauna on sandy beaches of the North Sea (The Netherlands, Belgium, France)

Sandy intertidal zones were analysed for the presence of meiofauna. The material was collected on six macro-tidal sandy beaches along the North Sea (The Netherlands, France, Belgium), in order to analyse the vertical and horizontal meiofaunal distribution patterns. Eleven higher meiofauna taxa (one represented by larval stage—Copepoda nauplii) were recorded. The maximum total meiofauna abundance was observed on the Dutch beach (4,295±911 ind. 10 cm⁻²) in the Westerschelde estuary, while the lowest values (361±128 ind. 10 cm⁻²) were recorded in France at the Audresselles beach. Meiofauna of the different localities consisted mainly of nematodes, harpacticoids and turbellarians. Nematodes numerically dominated all sampled stations, comprising more than 45% of the total meiofauna density. Meiofauna was mainly concentrated at the sand surface with about 70% present in the uppermost 5 cm. Meiofauna occurred across the entire intertidal zone. A clear zonation pattern in the distribution of meiofauna taxa across the beaches was observed. The present work suggests that designation of exposed sandy beaches as physically controlled (McLachlan 1988) does not explain their biological variability.     

Intertidal meiofauna of a high-latitude glacial Arctic fjord (Kongsfjorden, Svalbard) with emphasis on the structure of free-living nematode communities

Meiofauna communities of four intertidal sites, two sheltered and two more exposed, in Kongsfjorden (Svalbard) were investigated in summer 2001 at two different tidal levels (i.e. the low-water line and close below the driftline, referred to as mid-water (MW) level). A total of seven meiofaunal higher taxa were recorded with nematodes, oligochaetes and turbellarians being numerically dominant. Mean total meiofaunal densities ranged between 50 ind. 10 cm⁻² and 903 ind. 10 cm⁻². Our data showed a clear decrease in total meiofaunal densities with increasing coarseness of the sediment. Total meiofaunal biomass varied from 0.2 g dwt m⁻² to 2 g dwt m⁻² and, in general, was high even at low meiofaunal densities, i.e. larger interstitial spaces in coarser sediments supported larger meiofauna, especially turbellarians. The results on the vertical distribution of meiofauna contrasted sharply with typical meiobenthic depth profiles on other beaches, probably in response to ice-scouring and concomitant salinity fluctuations. Oligochaetes were the most abundant taxon, with a peak density of 641 ind. 10 cm⁻² at Breoyane Island. They were mainly comprised of juvenile Enchytraeidae, which prohibited identification to species/genus level. Nematode densities ranged between 4 ind. 10 cm⁻² and 327 ind. 10 cm⁻². Nematodes were identified up to genus level and assigned to trophic guilds. In total, 28 nematode genera were identified. Oncholaimus and Theristus were the most abundant genera. The composition of the nematode community and a dominance of predators and deposit feeders were in agreement with results from other arctic and temperate beaches. Nematode genus diversity was higher at the more sheltered beaches than at the more exposed ones. Low-water level stations also tended to harbour a more diverse nematode communities than stations at the MW level. Differences in nematode community structure between low- and MW stations of single beaches were more pronounced than community differences between different beaches and were mainly related to resources quality and availability.     

Composition and distribution of meiofauna,including nematode genera,in two contrasting Arctic beaches

The meiofauna of two tidal beaches, one exposed and one more sheltered, on Bjornoya (Bear Island) was investigated in summer 2000. Both meiofaunal densities and composition seem to be controlled by physical properties of the sediment, which in turn are controlled by exposure. The moderately and poorly sorted sediments in the sheltered beach were more abundant in terms of meiofaunal densities than the well sorted sediments in the exposed beach (254–481 individuals in 10 cm² vs 7–269 individuals in 10 cm², respectively). In total, seven higher meiofaunal taxa were found. Turbellaria were the numerically dominant taxon in the exposed beach. In the sheltered beach, Turbellaria also dominated, followed by Nematoda and Harpacticoida. The vertical distribution of the meiofauna was in accordance with what has been reported from other intertidal beaches. Nematoda were studied in detail and their densities ranged over 0.7–7.7 individuals in 10 cm² in the exposed beach and 2.7–186.0 individuals in 10 cm² in the sheltered beach. Nematodes were identified to genus level and a total of eight nematode genera were found. Sediment community respiration, measured as oxygen consumption, ranged between 2.3 cm³ O₂ m^–2 h^–1 in the exposed beach and 7.3 cm³ O₂ m^–2 h^–1 in the sheltered beach (respectively, the equivalent of 24 mg and 75 mg of organic carbon metabolised per day). Values from the sheltered site are within the range of results registered in much warmer localities.     

Evaluating the anesthetization and fixation efficacy of “soft” and “hard” freshwater benthic meiofauna: what is the best method for specimen preservation?

Sampling freshwater biological diversity is a challenge when it comes down to techniques for meiofauna fixation and preservation because this polyphyletic group of taxa is highly diverse. The aim of this study is to test the performance of three anesthetics (CO₂, MgCl₂ and low temperature) and three fixatives (formaldehyde 4 %; buffered formaldehyde 4 and 70 % ethanol) in the preservation of “soft” (gastrotrichs and rotifers) and “hard” (tardigrades and copepods) freshwater benthic meiofaunal assemblages. Due to these different morphological structures, we expected that treatment performance would vary among taxa in the quality of specimen fixation. Results revealed that the meiofaunal abundances of samples sorted alive or after the treatments with a coupling of anesthetics and fixatives were not different. However, preservation of specimens varied substantially among “soft” and “hard” meiofauna and among treatments. The use of 4 % buffered formaldehyde is highly recommended for freshwater meiofauna, while unbuffered formaldehyde should be avoided. Studies that have “soft” meiofauna as target organisms are recommended to use some type of anesthetic, although it is necessary to use a specific one for each taxon as they respond in different ways to different anesthetics.     

Abundance and composition of the sea-ice meiofauna in off-shore pack ice of the Beaufort Gyre in summer 2002 and 2003

We studied the abundance, biomass and potential ingestion rates of meiofauna in multi-year sea ice (MYI) of the Beaufort Gyre during two icebreaker expeditions in summers 2002 and 2003. Ice cores were taken at a total of ten stations and analyzed for ice temperature, salinity, chlorophyll a (Chl a), and ice meiofauna abundances. In 2002, ice was free of snow and covered with melt ponds. In 2003, snow still covered the ice and a slush-layer was found in the ice-water interface. The vertical distribution of Chl a mostly followed C-shaped curves with elevated concentrations at the bottom and top of the ice. Ice meiofauna was mainly restricted to the bottom 10 cm of the ice and was dominated by turbellarians, harpacticoid copepods and nematodes. The meiofauna abundances (range: 8–3,000 individuals m^–2) and Chl a concentration (range: 0.1–1.7 mg Chl a m^–2) were similar to estimates for MYI of the Transpolar Drift, but about 2 orders of magnitude below coastal fast first-year ice estimates. Calculated potential meiofaunal ingestion rate, based on allometric equations and volume estimates from the literature, was about 1% of published daily algal production rates and was thus unlikely to constrain algal biomass accumulation.     

污水排海对小型底栖生物丰度和生物量的影响

为了解污水排海对小型底栖生物丰度和生物量的影响,于2011年4、8、10、12月对青岛汇泉湾第一海水浴场中潮带一个排污口附近不同距离站位的小型底栖生物进行了春、夏、秋、冬4个季度的采样调查.结果表明： 研究区域小型底栖生物年平均丰度为(1859.9±705.1) ind·10 cm^-2,最高值出现在距离排污口20和40 m的站位S₂和S₃,分别为(2444.9±1220.5)和(2492.2±1839.9) ind·10 cm^-2,最低值出现在距离排污口0 m的站位S₁,为(327.9±183.2) ind·10 cm^-2.小型底栖生物的年平均生物量为(1513.4±372.7) μg·10 cm^-2.小型底栖生物在丰度和生物量上呈现明显的季节变化,最高值出现在春季,最低值出现在夏季.共鉴定出11个小型底栖生物类群,包括线虫、桡足类、多毛类、寡毛类、缓步动物、海螨、涡虫、介形类、等足类、甲壳类幼体及其他类.自由生活海洋线虫是最优势的类群,占总丰度的83.1%,其次为底栖桡足类,占12.8%.在垂直分布上,小型底栖生物在0~2 cm表层分布最多,向深层呈现递减趋势,冬季部分向下迁移.Pearson相关分析表明,小型底栖生物丰度和生物量与沉积物中值粒径和有机质含量呈极显著负相关.此外,旅游等人为扰动也是影响小型底栖生物数量及分布的因素.与历史资料中的同类研究结果进行了比较,并探讨了线虫与桡足类丰度的比值
在有机质污染监测中的适用性.     

Benthic seasonality in an intertidal mud flat at Kerguelen Islands (Austral ocean). The relationships between meiofaunal abundance and their potential microbial food

Summary Samples were taken weekly for one year at an intertidal mudflat at the Halage des Swains, Morbihan Sound, Kerguelen Islands, for meiofauna, their suspected microbial food (bacteria and diatoms) and associated chemical and physical factors. Organic carbon and nitrogen content, bacterial abundance and biomass, pigment content and daily primary production, were significantly correlated (Spearman rank) to the temperature. Meiofauna exhibited very high abundances (up to 14 000 ind./10 cm^–2) without seasonal trend but with distinct short term oscillations of population densities. No direct correlation occurred between meiofauna (85.9% nematodes and 10.8% copepods) and temperature. Total meiofauna abundance was positively correlated to bacterial biomass in the oxidized layer, to organic content below redox potential discontinuity layer, and negatively correlated to the hourly primary production. The data suggest that nematodes are correlated to bacterial biomass and organic content in the sediment. Effect of ambient temperature on development time of nematofauna could be described by a Belehradek function. Even though some correlations existed, this study shows that peaks of meiofaunal abundance are not correlated to potential food abundance variability. Thus, the limitation of meiofauna community and its annual pattern is reasonably governed by the development time and reproductive strategy of the few co-dominant species of the main taxa.     

Meiobenthos in mangrove areas in eastern Africa with emphasis on assemblage structure of free-living marine nematodes

A survey was conducted to examine spatial variations in the population density of major meiofaunal taxa and the assemblage structure of free-living marine nematodes within 5 mangrove areas on the west and east coast of Zanzibar. Meiofauna densities in surface sediments (0–5 cm) ranged from 205 to 5263 ind. 10 cm², being on average 1493 ind. 10 cm². Of the 17 major taxa recorded, nematodes dominated (64–99%) in all samples while harpacticoid copepods were usually second most abundant. Within all areas the numbers of meiofauna were very variable and significant differences among areas were only detected for oligochaetes and turbellarians. Densities of nematodes, harpacticoids, polychaetes and turbellarians were, however, significantly (P<0.001) higher at low water stations compared with mid and high water stations. Harpacticoids were negatively correlated with the numbers of fiddler crab (Uca spp.) burrows. Other correlations between environmental factors (grain size, temperature, salinity, oxygen tension, prop root density, fiddler crab burrows) and major meiofaunal taxa were non-significant. A total of 94 nematode genera were recorded from four mangrove areas. The most abundant and frequent genera were Microlaimus and Spirinia, followed by Desmodora and Metachromadora. Representatives of the genera most common in current study are found all over the globe. There was a high variation in nematode assemblage structure within and between sampling areas indicating the absence of a well defined nematode assemblage confined to mangrove areas. In a hypersaline area diversity was much reduced and where salinity was over 100%. the fauna was restricted to 3 nematode genera, Microlaimus, Theristus and Bathylaimus. Multidimensional scaling ordination (MDS) of the nematode genera separated samples taken from low water stations from other stations, the assemblage structure being significantly different at the low water stations. Numbers of selective deposit feeders were negatively correlated with average grain size and positively correlated with silt content.     

Temporal spatial distribution of benthic meiofauna in four beaches of the northern Havana shore

The temporal-spatial distribution of benthic meiofauna was evaluated in four beaches at the north coast of Havana, Cuba, from March 2003 to February 2004. We studied two urban beaches (Santa Fe and La Concha) and two tourist beaches (Mar Azul and Canasi). Monthly meiofauna samplings were taken by scuba-diving using with a syringe (inner diameter 2.5 cm), and physico-chemical parameters (grain size, interstitial salinity and water column salinity were recorded with standard equipment). Statistical analysis (MDS and ANOSIM) were performed. Depth and biotope kind were the same in the four beaches. Highest densities were obtained in Santa Fe (7,133.48 ind/10 cm2) while the lowest mean densities were found in Canasí (892.12 ind/10 cm2). We recorded 13 taxa; the dominant organisms in Santa Fe and Mar Azul were free-living marine nematodes. Copepods were the dominant organisms in La Concha and Canasí.     

Composition,distribution and biomass of meiobenthos in the Oosterschelde estuary (SW Netherlands)

Meiofauna composition, abundance, biomass, distribution and diversity were investigated for 31 stations in summer. The sampling covered the whole Oosterschelde and comparisons between the subtidal — intertidal and between the western-central — eastern compartment were made.Meiofauna had a community density ranging between 200 and 17 500 ind 10 cm^–2, corresponding to a dry weight of 0.2 and 8.4 gm^–2. Abundance ranged between 130 and 17 200 ind 10 cm^–2 for nematodes and between 10 and 1600 ind 10 cm^–2 for copepods. Dry weight biomass of these taxa was between 0.5–7.0 gm^–2 and 0.008–0.3 gm^–2 for nematodes and copepods respectively.The meiofauna was strongly dominated by the nematodes (36–99%), who's abundance, biomass and diversity were significantly higher intertidally than subtidally and significantly higher in the eastern part than in the western part. High numbers were positively correlated with the percentage silt and negatively with the median grain size of the sand fraction. The abundance and diversity of the copepods were highest in the subtidal, but their biomass showed an inverse trend being highest on the tidal flats.The taxa diversity of the meiofauna community and species diversity of both the nematodes and the copepods were higher in subtidal stations than on tidal flats. In the subtidal, the meiofauna and copepod diversity decreased from west to east, whereas nematode diversity increased.The vertical profile clearly reflected the sediment characteristics and could be explained by local hydrodynamic conditions.Seasonal variation was pronounced for the different taxa with peak abundance in spring, summer or autumn and minimum abundance in winter.Changes in tidal amplitude and current velocity enhanced by the storm-surge barrier will alter the meiofauna community structure. As a result meiofauna will become more important in terms of density and biomass, mainly due to increasing numbers of nematodes, increasing bioturbation, nutrient mineralisation and sustaining bacterial growth. A general decrease in meiofauna diversity is predicted. The number of copepods is expected to decrease and interstitial species will be replaced by epibenthic species, the latter being more important in terms of biomass and as food for the epibenthic macrofauna and fishes.     

Population fluctuation and vertical distribution of meiofauna in the Red Sea interstitial environment

The composition and distribution of the benthic meiofauna assemblages of the Egyptian coasts along the Red Sea are described in relation to abiotic variables. Sediment samples were collected seasonally from three stations chosen along the Red Sea to observe the meiofaunal community structure, its temporal distribution and vertical fluctuation in relation to environmental conditions of the Red Sea marine ecosystem. The temperature, salinity, pH, dissolved oxygen, and redox potential were measured at the time of collection. The water content of the sediments, total organic matters and chlorophyll a values were determined, and sediment samples were subjected to granulometric analysis. A total of 10 meiofauna taxa were identified, with the meiofauna being primarily represented by nematodes (on annual average from 42% to 84%), harpacticoids, polycheates and ostracodes; and the meiofauna abundances ranging from 41 to 167 ind./10 cm². The meiofaunal population density fluctuated seasonally with a peak of 192.52 ind./10 cm² during summer at station II. The vertical zonation in the distribution of meiofaunal community was significantly correlated with interstitial water, chlorophyll a and total organic matter values. The present study indicates the existence of the well diversified meiofaunal group which can serve as food for higher trophic levels in the Red Sea interstitial environment.     

广西防城港东湾红树林湿地春季小型底栖动物丰度与生物量

于2019年春季在广西防城港东湾红树林湿地,设置4个断面共13个站位采集沉积物样品,对小型底栖动物的类群组成、丰度和生物量进行研究。共鉴定出11个以上的小型底栖动物类群,分别为自由生活海洋线虫、桡足类、多毛类、寡毛类、介形类、等足类、双壳类、涟虫、海螨类、腹足类、枝角类和其他未鉴定类群;小型底栖动物总平均丰度为(10364±8012) ind·10 cm-2;线虫是绝对优势类群,占小型底栖动物总丰度的95.38%,平均丰度为(9886±7746) ind·10 cm^-2,其次为桡足类,占比为2.14%,平均丰度为(221±358) ind·10cm^-2;小型底栖动物的总平均生物量为(10502±7894)μg·10 cm^-2,各断面的生物量趋势依次为:断面3>断面2>断面1>断面4。     

Meiofaunal (re)colonization of the Arctic intertidal (Hornsund,Spitsbergen) after ice melting: role of wrack deposition

Intertidal meiobenthos of Hornsund—the southernmost fjord of Spitsbergen—was investigated between July and September 2005. Mean total meiofaunal densities ranged between 4.3 and 328 ind. 10 cm⁻². Nematode assemblages were impoverished in terms of the number of genera when compared with those from the western Spitsbergen coast (11 vs. 25–28 genera in total, respectively). It is suggested that severe environmental conditions in the southern part of Spitsbergen overcome the adaptation skills of many nematode species and hamper the establishment of a diverse community. Comparatively high nematode numbers on a beach subject to heavy macroalgal wrack input contrast sharply with numerically poor communities in sparse-wrack beaches (up to 315 vs. 31 ind. 10 cm⁻², respectively). It is suggested that the wrack input to the Arctic beach may substantially influence the richness and composition of the intertidal meiobenthic community. Nematode assemblages were dominated by extreme colonizers: Geomonhystera disjuncta and rhabditids. Their relatively high densities in beach sediments recorded at the beginning of July indicate their ability to recover rapidly after the winter period and to effective (re)colonization of the intertidal habitat just after the ice melt. Average concentration of rhabditids and monhysterids associated with macroalgal wrack deposited on the upper shore was as high as 52 × 10³ individuals per gram of the substrate. It is hypothesized that nematodes can play a substantial role in the wrack decomposition in the Arctic intertidal.     

Description of intertidal macro- and meiobenthic assemblages in Maxwell Bay, King George Island, South Shetland Islands, Southern Ocean

The intertidal benthic fauna of the Antarctic coastal areas is largely unknown and has long been thought to be absent or, at most, to be scarce. Since climate changes cause a progressive expansion of ice-free intertidal soft-bottom areas, the fauna of these areas could serve as essential criterion to evaluate the kind and dimension of such changes. We therefore investigated the faunal composition of the intertidal soft-bottom area of Maxwell Bay (King George Island, South Shetlands) in December 2006. Samples for quantitative analyses were taken from the soft-bottom during low tide using a plastic corer. We performed detailed analyses of the soft-bottom beneath a cobble layer, while hard-bottom and macrophytes were only sporadically investigated. Approximately 5,000 specimens were collected of which polychaetes (37.3 ± 7.6 (max. 44.7) ind. × 100 cm^?³) and harpacticoids (28.9 ± 28.5 (max. 104.0) ind. × 10 cm^?³) were the most abundant macro- and meiofauna taxa of the soft-bottom, followed by oligochaetes, nematodes, mollusks, and amphipods. A total of 58 macrofauna species were registered, of which 27 were identified only to a supraspecific level. The most species-rich macrofauna taxon was polychaetes with at least 24 species, followed by amphipods, gastropods, and oligochaetes with 6 species each. The harpacticoid copepods were represented by 15 families with more than 30 species. In summary, we show that the Antarctic intertidal soft-bottom is densely populated by macro- and meiofauna and that it deserves closer attention in the future to determine whether it can indeed serve as an indicator of the effect of climate changes on the Antarctic coastal areas.     

Meiofauna distribution in Martel Inlet, King George Island (Antarctica): sediment features versus food availability

The meiofauna density in Martel Inlet, Admiralty Bay, King George Island (Antarctica) was studied in order to better understand the spatial patterns of meiofauna distribution in shallow polar seas. Sampling was undertaken by scuba-diving at 15 m depth at 7 stations during the summers of 1996/1997 and 1997/1998. The meiofauna was dominated by nematodes (>60%), followed by copepods, nauplii and polychaetes. The mean densities found during the 2 years studied (4.09 and 3.5᎒⁶ ind. m^-2) suggest that the shallow area of Martel Inlet is characterized by higher numbers of meiofaunal organisms than are found in other ecosystems, which is in agreement with other meiofaunal studies carried out in polar areas. It may be concluded that it is mainly the sedimentary features that influence the meiofauna distribution. However, food availability must contribute to the support of the higher meiofauna densities found in the inlet.     

Distribution and abundance of soft-sediment meiofauna and a predatory goby in a coral reef lagoon

Spatial patterns in the abundance of the softsediment meiofauna and a predatory goby, Valenciennia longipinnis, were examined in the lagoon of One Tree Reef (Great Barrier Reef). The study provided a quantitative framework to assess the importance of physical factors on and predator prey interactions between the meiofauna and V.longipinnis. Patterns of abundance were examined at two spatial scales: among four habitats (100's of m apart) and among sites (10's of m apart) within habitats. Of the four major constituents of the meiofauna (harpacticoid copepods, nematodes, polychaetes and oligochaetes), gut analyses showed that harpacticoid copepods were the primary prey of V.longipinnis. Spatial patterns of meiofaunal abundance in the lagoon were taxon specific. Polychaetes and harpacticoid copepods exhibited significant differences among habitats. Within habitats, however, polychaetes exhibited significant differences between sites whereas copepods were uniformly distributed. Abundances of nematodes and oligochaetes did not differ between habitats. Densities of nematodes differed significantly between sites while the number of oligochaetes were similar at both spatial scales. V.longipinnis was more abundant in shallow habitats than in deep ones. This study suggests that sediment type may be an important factor influencing the distribution of both the goby and the meiofauna. V.longipinnis and two of the four meiofaunal taxa (harpacticoid copepods and polychaetes) were more abundant in the shallow habitat with fine-grained sediments. There was no significant difference between abundances of meiofaunal taxa in sites where V.longipinnis was present or absent. Overall, more fish occurred in the habitat which had the highest densities of harpacticoid copepods.     

The primary production of phytoplankton in the restored Maltañski Reservoir in Poland

Patterns in composition, abundance and diversity of the annelid fauna (Polychaeta and Oligochaeta) in 22 sandy beaches in Iceland were explored. The effect of exposure on annelid distribution was studied. A total of 5651 annelids were recorded from 160 core samples. Oligochaetes (chiefly Tubificidae) dominated the annelid assemblage whereas polychaetes represented a minor fraction. Polychaetes were relatively more abundant in exposed than in sheltered beaches, contrary to oligochaetes. Meiofaunal polychaete species were also more abundant in exposed than in sheltered beaches. Southwest beaches seemed more diverse in annelid species than northern ones. Annelid diversity did not differ between sheltered and exposed sites, but higher diversity was attained in fine sands at sheltered areas. Cluster analysis revealed large differences between beaches in the annelid community composition. The general patterns found suggest that beach exposure is a major factor conditioning macro- and meiofaunal polychaete and oligochaete distribution along the Icelandic coast.     

An ecological and economic review of meiofauna as food for fish*

After briefly reviewing the evidence that meiofauna are an integral part of the complex food web of invertebrate infaunal and epifaunal organisms, it is shown that, at least in intertidal and shallow subtidal habitats, meiofauna are an important food for the small (30–60 mm) juveniles of some commercially important fishes (flatfish and salmonids) or for fish which are themselves food for commercial species. The evidence that fish feed preferentially on a few species of harpacticoid copepod rather than on the numerically dominant meiofaunal taxa is presented and discussed. It is argued that, in addition to benthic copepods being energetically efficient as food for fishes, it is differences in the activity and availability between major taxa of meiofauna as they relate to the feeding strategies of the fish which go a long way to explaining this apparent general preference of fish for harpacticoid copepods rather than nematodes. From literature estimates of consumption rates, it is concluded that the supply of meiofaunal food to juvenile fish is unlikely to be limiting although this may not be the case in some shallow subtidal muddy sand habitats. Whilst it is recognized that fish predation may influence the magnitude of the seasonal peaks in numbers, predation is not the principal cause of seasonal fluctuations in harpacticoid copepod species abundances. The effects of predation on other aspects of community structure is unknown. Finally, the possible role of meiofauna in mariculture systems is briefly discussed.     

The meiobenthos of five mangrove vegetation types in Gazi Bay,Kenya

The vertical distribution of meiofauna in the sediments ofAvicennia marina,Bruguiera gymnorrhiza,Ceriops tagal,Rhizophora mucronata andSonneratia alba at Gazi Bay (Kenya), is described. Seventeen taxa were observed, with highest densities in the sediments ofBruguiera (6707 ind. 10 cm^–2), followed byRhizophora (3998 ind. 10 cm^–2),Avicennia (3442 ind. 10 cm^–2),Sonneratia (2889 ind. 10 cm^–2) andCeriops (1976 ind. 10 cm^–2). Nematodes accounted for up to 95% of total densities; other common taxa were copepods, turbellarians, oligochaetes, polychaetes, ostracods and rotifers. High densities occurred to about 20 cm depth in the sediment. EspeciallyCeriops sediments show still high densities of nematodes (342 ind. 10 cm^–2) and copepods (11 ind. 10 cm^–2) in the deepest layer (15–22 cm). Particle size and oxygen conditions were major factors influencing meiobenthic distribution;Uca burrows had a major impact on distribution and abundance of meiofauna.     

Non-Linear Interactions Determine the Impact of Sea-Level Rise on Estuarine Benthic Biodiversity and Ecosystem Processes

Sea-level rise induced by climate change may have significant impacts on the ecosystem functions and ecosystem services provided by intertidal sediment ecosystems. Accelerated sea-level rise is expected to lead to steeper beach slopes, coarser particle sizes and increased wave exposure, with consequent impacts on intertidal ecosystems. We examined the relationships between abundance, biomass, and community metabolism of benthic fauna with beach slope, particle size and exposure, using samples across a range of conditions from three different locations in the UK, to determine the significance of sediment particle size beach slope and wave exposure in affecting benthic fauna and ecosystem function in different ecological contexts. Our results show that abundance, biomass and oxygen consumption of intertidal macrofauna and meiofauna are affected significantly by interactions among sediment particle size, beach slope and wave exposure. For macrofauna on less sloping beaches, the effect of these physical constraints is mediated by the local context, although for meiofauna and for macrofauna on intermediate and steeper beaches, the effects of physical constraints dominate. Steeper beach slopes, coarser particle sizes and increased wave exposure generally result in decreases in abundance, biomass and oxygen consumption, but these relationships are complex and non-linear. Sea-level rise is likely to lead to changes in ecosystem structure with generally negative impacts on ecosystem functions and ecosystem services. However, the impacts of sea-level rise will also be affected by local ecological context, especially for less sloping beaches.