Macrobenthic Assemblages Research Articles

Biomonitoring application using macrozoobenthic assemblanges at coastal area of Menjangan Besar Island, Kepulauan Karimunjawa, Indonesia

The macrozoobenthic structure inhabiting marine ecosystem may be used as a bioindicator of changes in aquatic environmental disturbance. This study is aimed to assess environmental disturbance by application of biomonitoring using macrozoobenthic assemblages at coastal area of Menjangan Besar Island, Kepulauan Karimunjawa, Indonesia. The macrozoobenthic assemblages were assessed at two sampling locations, i.e. floating net cage of monoculture and reference areas. Each sampling location consisted of three stations with three replicates for each station. The samples were taken in two sampling times, i.e. August and November 2018. Data of abiotic parameters included the composition of organic matter content, sediment substrates, DO, pH, salinity, temperature, and water current. Sediments were sampled using Ekman grab from 15 m deep. The relationship between biotics (macrozoobenthos) and abiotics (physical-chemical factors) was assessed using a non-parametric multivariate procedure (BIO-ENV; Primer 6.1.5). Macrobenthic assemblages consisted of 89 species with the total abundance of 50,071 individuals/m2, consisting of 52 families and 4 classes of macrozoobenthos. The values of indices were ranging from 2,54-3,40 for diversity index (H'), 0,99 for Pielou’s evenness index (e’), and 0,09-0,17 for dominance index (C). The most common classes were a member of Gastropods and bivalves. Diversity and evennes indices exhibited differed by location (monoculture vs reference) and time sampling. Fluctuation of macrobenthic structure was considered as a results of environmental changes spatially and temporally, especially sediment composition and food availability as the form of organic matter. Nitrogen and silt were the most chemical and physical factors influencing the structure of macrozoobenthos (r = 0,632; BIO-ENV).

Exploring overlooked components of remote South‐east Pacific oceanic islands: Larval and macrobenthic assemblages in reef habitats with distinct underwater soundscapes

Abstract Identifying the diverse assemblage of species inhabiting rocky and coral reef habitats in isolated oceanic environments, and the important sound cues emitted from the reef, are crucial components to understand how species locate suitable habitats for the completion of their life‐cycle and, thus, the functioning of these vulnerable ecosystems. Recent field information suggests that the majority of reef biodiversity comprises small cryptic invertebrates; however, knowledge on these small components is extremely scarce. The present study used light attraction methods to explore the diversity of larval, post‐larval and macrobenthic cryptic fauna, and hydrophones to characterize the natural soundscape of rocky and coral reef habitats at the Robinson Crusoe island (Juan Fernandez Archipelago; 33°38′S, 78°50′W), and Rapa Nui (Easter Island; 27°7′S, 109°21′W), respectively. Pelagic collections found important site‐specific patterns and identified two main species assemblages: early‐life stages (e.g. eggs, larval and juvenile stages of crustaceans, molluscs, and fishes) and emerging macrobenthos (e.g. demersal zooplankton such as peracarid crustaceans, ostracods, copepods, and polychaetes), with the latter contributing between 73 and 98% to the total catches. The soundscape records showed marked differences among sites and seasons at Robinson Crusoe island, with variable differences found between day and night. However, at Rapa Nui, there were no differences between sites, but the ambient sound was higher at night possibly due to higher snapping shrimp activity. This information highlights the importance of considering small‐scale (site‐to‐site) patterns when evaluating overlooked components of diversity (i.e. biological or acoustic) in oceanic habitats, and provides the basis for understanding the importance of natural noise in the settlement of most reef‐associated species, crucial features for the conservation of these remote and vulnerable ecosystems.

Do different sympatric seagrasses support macrobenthic faunas of differing composition, abundance, biodiversity or patchiness?

Intertidal macrobenthic assemblages associated with monospecific areas of different sympatric though not syntopic seagrasses [Cymodocea, Halodule, Zostera and Halophila] were investigated in Moreton Bay across a continuous <0.12 ha seagrass area with minimal potentially-confounding environmental variables. Results indicated patterns of unchanging faunal metrics across seagrass types (abundance, richness, diversity, evenness, taxonomic distinctness, and patchiness) but variation in relative proportions of dominant taxa, particularly microgastropods (abundant in Zostera, insignificant in Cymodocea and Halodule). Although assemblage composition varied, faunal dissimilarities (except with Zostera) were very low and of similar magnitudes within and between different 'host' seagrasses. This suggests that such macroecological faunal characteristics are not consequent on the precise local ecosystem engineer but largely reflect those of a common pool of locally available species, so that the differences in animal abundance and biodiversity described in some studies relate not directly to features inherent in the different seagrasses, but to associated habitat variables.

Efecto de los efluentes cloacales sobre el ensamble macrobentónico submareal en un estuario urbano de la Argentina

Fil: Fiori, Sandra Marcela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Instituto Argentino de Oceanografia. Universidad Nacional del Sur. Instituto Argentino de Oceanografia; Argentina. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia; Argentina

Assessment of environmental status of coastal mangrove area using macrobenthic assemblages: a study case at Tapak Mangrove area, Semarang, Central Java

Macrobenthic structure can be used as a bioindicator in determining the level of disturbance in water ecosystem through their composition, presence or absence spatially and temporally as apart of ecological management. Tapak is a coastal area of Semarang City, Central Java, Indonesia that has potency as an ecotourism area for integrated aquaculture at mangrove area. On the other hand, industrial activity around Tapak coastal area may lead to a degradation of the ecological function of that area. This study aims to assess environmental status at Tapak Mangrove Area through the macrobenthic structure in space and time. Purposive random sampling method was applied, consisting five sampling stations with 3 replicates between March to May 2018. Sediment samples were taken by using Ekman grab and were analyzed through the stages of fixation, rinsing, sieving, preservation, sorting, identification, and enumeration. The biotic parameters observed were the macrobenthic community structure, including species composition, abundance, and diversity, evenness, and dominance indices. Physico-chemical parameters of the water and sediment were measured every month. The Early Warning System (EWS-3SWJ) software was used to assess the level of environmental disturbance at each station. The total of 15 species of macrobenthic assemblages were found. The most common species were Telescopium telescopium, Cerithidea cingulata, and Metapenaeus sp.. The diversity of macrobenthos was considered low at all sampling stations (H’ = 0,56 – 1,52), with marked variability in dominant taxa (D = 0,21 – 0,71). Further analysis using the EWS-3SWJ showed that the environmental status of the Tapak Mangrove Area is categorized as slightly disturbed areas.

Macrobenthic assemblage structure and distribution at the Boojagh Marine National Park, Southern Caspian Sea, Iran.

Although macrobenthic assemblages are considered as major players in many ecosystems around the world, the ecology of Caspian Sea macrobenthos is currently understudied. This study describes the species composition and quantitative distribution of macrobenthos in the southern Caspian Sea and relates the distribution to seasonal changes at three depths (1, 5 and 10 meters) on the Boojagh Marine National Park (BMNP) coast in the southern Caspian Sea between the summers of 2015 and 2016. To investigate the distribution of macrobenthos in BMNP, the data of 450 samples were analyzed. In this study sixteen species were identified: Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carausui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Nais sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor, Amphibalanus improvisus. Among them, the non-indigenous C. glaucum was the dominant species, accounting for 27% of the total abundance and in descending order P. grimmi with 14.4%, A. improvisus with 8.7%, M. lineatus with 7.9%, Nais sp. with 7.5%, N. carausui with 5.2%, P. motasi with 5%, S. gynobranchiata with 4.5%, H. invalida with 5%, M. Caspica with 3.1%, P. sowinskyi with 2.5%, O. caspius with 2.4%, A. kolesnikovi and H. diversicolor with 1.8%, S. gracilis with 1.6% and P. pectinatum with 1.5% were in the next rank. Significant differences in abundance across the sixteen species were observed among depths and seasons. This study highlights the potential consequences of established non-indigenous species in the southern Caspian Sea.

Nestedness and turnover unveil inverse spatial patterns of compositional and functional β‐diversity at varying depth in marine benthos

AbstractAimThe two additive components of β‐diversity, namely turnover and nestedness, reflect the two basic mechanisms underlying the overall change in species identities across the landscape, the replacement of species or their loss, respectively. Analogously, functional turnover and nestedness express the replacement or loss of functional traits associated with variations in community composition. However, the extent to which patterns of compositional and functional nestedness and turnover may overlap, or diverge, is still uncertain in marine environments. Here, patterns of turnover and nestedness were quantified in marine benthic assemblages in order to assess their relative contribution to spatial patterns of compositional and functional β‐diversity.LocationMediterranean Sea, NE Ionian Sea, Ionian Archipelago.MethodsIn this study, we investigated patterns of dissimilarity in species and functional trait composition in subtidal macrobenthic assemblages from Mediterranean islands in order to quantify compositional and functional β‐diversity among islands, determine the relative contributions of turnover and nestedness, and compare β‐diversity patterns occurring in shallow and deeper reefs.ResultsWe found a complex relationship between functional and compositional β‐diversity at varying depth. At 5 m, species and functional trait dissimilarity largely overlapped, with turnover being the dominant component in both cases. At 15 m, compositional β‐diversity was mostly due to turnover, with a negligible contribution of nestedness, whereas the opposite occurred for functional β‐diversity. Partitioning β‐diversity components revealed this discrepancy and the presence of functional hotspots, which would remain unnoticed analysing the overall compositional and functional β‐diversity.Main conclusionsOur findings may have profound implications for the optimization of conservation planning, stressing the need for assessing habitat‐dependent idiosyncrasies in components of functional and compositional β‐diversity for a more comprehensive picture of possible protection scenarios that, besides structure, may also allow preserving the functioning of marine communities.

Hydrodynamic Conditions Effects on Soft-Bottom Subtidal Nearshore Benthic Community Structure and Distribution

This study assesses the impacts of wave action and freshwater outflow on soft-bottom benthic macrofauna spatial distribution and temporal stability along the highly exposed French Basque coast. Sediment characteristics and macrofauna abundance have been seasonally investigated during two years for nine stations located at the same (6 m) depth and spread over three subtidal sites showing distinct exposure levels. Wave climate has been determined through an operational numerical model. A total of 121 taxa were recorded, gathered in three main faunal assemblages, as revealed by classification and ordination methods. Non-parametric multivariate multiple regression (distance-based linear model) showed that the variations in macrofaunal distribution can be explained by hydrodynamic conditions. Wave exposure strongly linked to estuarine inputs were the most relevant abiotic factors influencing distributional patterns and functional structure as described by biological traits analysis. Despite the influence of these abiotic variables affecting sedimentary dynamics, seasonal stability was observed in macrobenthic assemblages composition suggesting an ability to recover from natural disturbances such as (e.g.) winter storms. In this way, these results provide baseline knowledge for future ecosystem and resource management in shallow subtidal areas strongly exposed to swell and freshwater outflow where soft-bottom macrozoobenthic communities are less frequently studied.

Macrofaunal communities in the Gioia Canyon (Southern Tyrrhenian Sea, Italy)

Submarine canyons play pivotal roles in the physical, biological and ecological processes of coastal areas, especially in closed or semi-closed basins as the Mediterranean Sea, influencing the biodiversity and the abundance of the benthic fauna. On February 2013, during the Tyrrhenian Gravity Flows (TyGraF) campaign, samples have been collected along the Gioia Canyon Basin (Italy) with the aim to describe the taxonomical composition and the abundances of the macrobenthic assemblages, filling the gap of knowledge in this area. A total of 93 taxa were identified, and the Annelida was the phylum with the highest number of specimens and most diversified (46 taxa). The polychaetes Sternaspis scutata, Prionospio cirrifera and Monticellina sp., the bivalves Thyasira sp.1 and Saccella commutata and the amphipods belonging to the genera Ampelisca and Harpinia showed the highest densities in the studied area; however, results suggest low values of the abundances of the macrobenthos if compared with those generally reported for other canyons, both inside and outside the Mediterranean Sea. The marine biotic index (AMBI) highlights that the canyon system and the surrounded area were slightly disturbed and characterized by a high percentage of tolerant taxa. This study is the first baseline for future analyses of the macrobenthic communities of this area.

Environmental and Benthic Community Patterns of the Shallow Hydrothermal Area of Secca Delle Fumose (Baia, Naples, Italy)

The occurrence of hydrothermal vent ecosystems at Secca delle Fumose, Pozzuoli Bay (Gulf of Naples), represented an opportunity to study the benthic assemblages under the thermal stress of hydrothermal emissions in a very shallow environment (9 – 14 m water depth). In autumn 2016, the macrobenthic community was sampled by scuba divers at four sites located in the Baia Underwater Archaeological Park. Two sites were characterized by vent emissions (one with white bacterial mat scattered on the bottom and one with a yellow substrate around a geyser opening) and two at about 100 m away, used as control. Sediment and interstitial water environmental variables were measured to determine their influence on the structure of macrobenthic assemblages. A total of 1,954 macrofaunal individuals was found, characterized by great differences in abundance and species richness among sites. This pattern was correlated to the dominance of a particular set of variables that drastically change in a very small spatial scale, from one site to another. The control sites, characterized by the highest percentage of gravel in the sediments (19.67±2.6%) and normal level of major ions such as Ca2+, K+ and Mg2+ in the interstitial waters, showed the highest values of sinecological indices. The “white” hydrothermal site exhibited the lowest species richness, abundance and species diversity, influenced by low pH values (~7.6), high temperatures (~37.53°C) and by the highest total organic carbon content (TOC 34.78%) in the sediment. The “yellow” hydrothermal site, with sediment TOC equal to 30.03% and interstitial sulphide ions measuring 130.58 ppm, showed higher values of sinecological indices than those recorded at the “white” site. Therefore, taxonomic analysis revealed a high turnover between control and vents sites. This highlights the preference for hydrothermal vents by a few resistant species, such as the gastropod Tritia cuvierii and the polychaete Capitella capitata, confirming the role of the latter species as opportunistic in extreme environments like Secca delle Fumose.

Small-Scale Effects of Offshore Wind-Turbine Foundations on Macrobenthic Assemblages in Pinghai Bay, China

ABSTRACT Lu, Z.; Zhan, X.; Guo, Y., and Ma, L., 2020. Small-scale effects of offshore wind-turbine foundations on macrobenthic assemblages in Pinghai Bay, China. Journal of Coastal Research, 36(1),...

Effects of an experimental oil spill on the structure and function of benthic assemblages with different history of exposure to oil perturbation

The present study compared the short-term effects of a diesel oil spill on the strucure and function of nematode and macrobenthic assemblages between tidal flats with different history of exposure to oil perturbation. A manipulative field experiment was conducted, where oil exposed treatments were contrasted with controls, during four successive times, two before and two after the oil spills. During the oil spill the death and the presence of diverse debilitated macrofaunal organisms were observed in the oil treatments. However, 24 h later no significant changes were identified, suggesting that the impacted plots were quickly recolonized. Nematode assemblages showed a decrease in overall density and an increase of r-strategist traits such as non-selective deposit feeders and colonizers at perturbed treatments from one of the historically non-perturbed tidal flats. We discuss the mechanisms responsible by distinctive patterns of response observed between the two benthic components.

Effects of diesel oil spill on macrobenthic assemblages at the intertidal zone: A mesocosm experiment in situ

The oil spill accidents may drastically impact the environment and ecosystem at intertidal zones. The spilled oil will penetrate the sediments and accumulate to cause lethal or sublethal effects on the benthic invertebrates. An M-BACI experiment was manipulated in situ to assess the ecological responses of benthic macrofauna to different degrees of diesel oil spill. Both biotic and abiotic parameters were studied for 126 days, subjected to both “pulse” and “press” oil contaminations. The content of aliphatic hydrocarbons (displayed as ratios of n-C17/Pr and n-C18/Ph) slightly dropped then continuously existed in the sediment during the experiment time. The macrofaunal assemblage structures were dramatically altered in species number, abundance and biomass. In general, it takes longer time for the macrofauna assemblages to recover under high concentration oil spill than that under low concentration. Our results highlight the diversified strategies for survival and recolonization among dominant species, which distinguish themselves between: i) tolerant species, ii) opportunistic species, and iii) equilibrium species.

New Barremian Macroinvertebrates from the Huitrín Formation, Mendoza Province (Argentina) and Their Paleoecological Implications

The marginal-marine, low-energy, carbonate ramp deposits of the La Tosca Member (Huitrin Formation, Barremian) in southern Mendoza Province, Argentina, bear an abundant though low-diversity macrobenthic invertebrate fauna that is scarce or absent in the outcrops of the unit in the Neuquen Province. Here we describe new taxa from the Quebrada del Gastropodo and Ranquil 1 sections and provide taxonomic revisions for other key faunal elements. The species discussed herein are the gastropods Paleoanculosa macrochilinoides (Doello-Jurado), Provalvata minor sp. nov., and Provalvata maior sp. nov., the bivalve Rutitrigonia cintarojensis sp. nov., and the serpulid Parsimonia aff. laevis (Goldfu?). Additionally, in order to analyze the observed changes in faunal content along the studied section, a paleoecological analysis was performed combining estimation of diversity indices and the paleoautoecology of the fauna recorded in Quebrada del Gastropodo. Three macrobenthic assemblages were qualitatively recognized in the field; from base to top: 1) Paleoanculosa macrochilinoides, 2) serpulid-gastropod, and 3) bivalve-serpulid assemblages. Species richness and equitability increase upwards. This trend suggests a reduction in environmental stress from bottom to top. The first two assemblages indicate settings with fluctuating environmental parameters, whilst the third points to higher environmental stability. Euryhaline taxa dominate, whilst stenohaline species are scarce or absent in the lower two thirds of the succession. The nature of the stress is interpreted herein to be mainly related to high-frequency salinity variations, especially in the first and second assemblages in which temporal deviations from euhaline to meso-brachyhaline and brachyhaline conditions are hypothesized.

Ongoing ocean warming threatens the rich and diverse macrobenthic communities of the Antarctic continental shelf

Global warming is heating the Antarctic circumpolar deep water (CDW), which comes into direct contact with the diverse and abundant macrobenthic communities thriving on the continental shelf of the Weddell Sea (WS). A set of 16 current meters deployed along more than 3000 km coastline revealed that tidal currents drive CDW intrusions onto the WS continental shelf and they can increase the temperature near the seabed by ~2.7 °C. The ongoing ocean warming trend may expose macrobenthic assemblages to ambient temperatures >2 °C by the end of the century with dramatic consequences for communities which have evolved during millions of years in near geophysical isolation under rather constant environmental conditions with temperatures <0 °C. These stenothermal communities have long generation times (therefore, reduced opportunity to mutate) and require hundreds of years for adaptation.Results from 135 benthic stations along the study area showed that macrobenthic communities in the southeastern section of the WS are the most vulnerable to the increase of temperature near the seabed given their high component of sessile organisms. Besides a dramatic marine biodiversity loss, the eventual demise of these communities, which provide habitat structure for a large number of species that can build up >87 g C m−2, will cause the liberation of thousands of tons of carbon to the environment. Macrobenthic communities colonizing the recently opened shelf in the Larsen A and B bays may not have the chance to reach the type of mature assemblage inhabiting the eastern WS shelf. The highest temperatures derived from CDW intrusions were recorded in the Filchner-Ronne region, suggesting that the consequences of the thermal impact could develop faster here than in the rest of the WS. Thus, these macrobenthic communities may show the effects of warming earlier than those thriving in other regions of the WS shelf. Global warming seriously threats the abundant and highly diverse macrobenthic communities of the Antarctic continental shelf.

Macrofaunal spatial distribution and community structure in a lagoon without a river discharge (the Oualidia lagoon, NW Morocco)

AbstractThe assemblage structure and spatial distribution patterns of macrobenthic communities according to environmental conditions were analysed through five samplings carried out at 14 intertidal soft sediment stations in the Oualidia lagoon (NW Morocco). A total of 89 macrobenthic taxa were collected, amounting to 55.188 specimens. Molluscs, polychaetes and arthropods were the most species‐rich groups. The snail Peringia ulvae was the most dominant species, especially abundant in the mid‐ and upper lagoon sections (nearly 64% of the total specimens gathered), followed by the mollusc Scrobicularia plana (10%). Diversity values were generally low (&lt;3 bit) pointing out the high dominance by few species. Multivariate analyses clearly distinguished three distinct macrobenthic assemblages, successively distributed from lagoon inlets towards inner parts. Nevertheless, each assemblage was found in particular habitat types and had a specific species composition in response to different environmental characteristics. (a) The Scolelepis fuliginosa community occupied sandy substrates at the lower section of the lagoon with stronger marine influence and, (b) the P. ulvae community lived in sandy‐muddy substrates, including two sub‐communities dominated, respectively, by Cerastoderma edule, S. plana and Tritia pfeffeiri inhabiting the middle section and S. plana the upper section. The combination of salinity, temperature, pH and silt content was identified as the major environmental variable subset with the highest correlation with the observed macrofaunal patterns and silt fraction as the single best correlated variable. The results demonstrated significant spatial differences in macrobenthic assemblage structure and composition along environmental gradients in spite of the absence of direct freshwater river inflow.

Shipwrecks and underwater objects of the southern Baltic – Hard substrata islands in the brackish, soft bottom marine environment

Objects of anthropogenic origin submerged in the sea, such as shipwrecks, may induce significant environmental changes in their close proximity. There may be more than 100 000 shipwrecks in the Baltic Sea, however to date, their effects on biodiversity by the introduction of large hard substrates in this typically low-evenness, species-poor ecosystem have received little attention. This study compared separately macrobenthic assemblages found on three different objects (an old torpedo house, a former submarine and a minesweeper) lying at various depths (2–21 m) in Puck Bay (the Gulf of Gdańsk, Baltic Sea), and corresponding assemblages in soft sediments from their close (5 m away) and far vicinity (50 m away). A total of 26 taxa of macrobenthic algae, vascular plants and fauna were recorded. Nineteen species were found directly on the study objects. Nine species among them were only found on the submerged objects but none was substrate specific. At two locations clear differences in the assemblage structure between seabed in the close proximity of submerged objects and the seabed located farther apart were noted. Higher species richness, abundance and diversity (measured as Shannon-Wiener H′) was recorded only in the location of the deepest object. Its high similarity (both in terms of the assemblage structure and S, N, H’) with the closest neighbouring sediments may indicate a direct impact of the object on the surrounding seabed. The submerged objects generally supported a two - three times higher number of species and a ∼25 times higher number of individuals (but not diversity) than the soft bottom in the vicinity. The shallowest object lying within the euphotic zone hosted the most species rich (on avg. 10 species/144 cm2) and abundant (on avg. 379 ind./144 cm2) assemblages. Differences in the assemblage structure found between different objects are most likely associated with depth related environmental variables. The results of the study can serve as a baseline for future investigations and for evaluation of local ecological effects of the artificial reef concepts, breakwaters and offshore wind farms.

Plant Part Age and Size Affect Sessile Macrobenthic Assemblages Associated with a Foliose Red Algae Phycodrys rubens in the White Sea

Facilitation by foundation species commonly structures terrestrial and marine communities. Intraspecific variation in individual properties of these strong facilitators can affect the whole suite of the dependent taxa. Marine macroalgae often act as ecosystem engineers, providing shelter and substrate for numerous associated organisms. Epibiosis of foliose red algae, however, remains underexplored, especially in the high latitudes. Here we studied sessile macrobenthic assemblages associated with a foliose red algae Phycodrys rubens in the White Sea (66° N) shallow subtidal, and the effect of individual plant properties on their structure. The blades of P. rubens develop annually, and it is possible to tell the young (usually larger) plant parts from the old ones. We hypothesized that epibenthic community structure depends on plant part age and size. We examined epibiosis on 110 plants at two sites, and the results generally supported our hypotheses. Old plant parts were several times smaller, and had higher total cover than young parts. Sponges strongly dominated the epibiosis on old parts, and young parts were dominated by polychaetes and bryozoans. Plant part surface area negatively correlated with total cover on young parts, while on old parts the relatioship was location-specific. On young parts the relative abundance of a polychaete Circeis armoricana increased with surface area, and the proportion of sponges decreased. The patterns indicate that epibenthic community structure is linked to the demography of an ecosystem engineer.

Local patchiness of macrobenthic faunal abundance displays homogeneity across the disparate seagrass systems of an estuarine bay

Spatial variation in the degree of local patchiness of macrobenthic assemblage abundance was assessed across the 16 km2 warm-temperate Knysna estuarine bay (South Africa) where the seagrass Zostera (Zosterella) capensis grows under a broad spectrum of environmental conditions and supports invertebrate assemblages at a wide range of local density (<2000->320000 ind. m−2). Macrobenthic assemblage abundance at all 27 representative sites examined displayed low-level but highly-significant spatial patchiness (mean Lloyd's index, IP = 1.148). Except at high tidal levels, however, the magnitude of this local patchiness did not vary statistically across the system (CV 4.3%) regardless of assemblage abundance, location or species composition. Patchinesses well within ±1 standard deviation of Knysna's value also characterise an equivalent Z. (Zosterella) capricorni assemblage in subtropical Queensland (IP 1.169) and another, Z. (Zosterella) noltei, assemblage in cool-temperate England (IP 1.135), suggesting that at local scales intertidal dwarf-eelgrass macrobenthic abundance displays a characteristic level of patchiness.

The comparison of distribution patterns of macrobenthic assemblages adjacent floating net cage areas at Karang Lebar Island, Jakarta: a multivariate approach

Water and sediment ecosystems are often influenced by fish farming activities especially organic matter that lead to organic enrichment. The macrobenthic community is one of the benthic organisms that can be used as bioindicator to detect disturbances in aquatic environments. The purpose of this study was to compare the distribution patterns of macrobenthic assemblages adjacent to floating net cages situated at Karang Lebar Island, Jakarta using a multivariate approach. Three sampling locations were assessed, each with three stations and three replicates. Each location consisted of a floating net cage of monoculture, a floating net cage of IMTA (Integrated Multi-Trophic Aquaculture), and a reference site at Karang Lebar Island, Kepulauan Seribu, DKI Jakarta. All data concerning macrobenthic presence was expressed using diversity (H’), evenness (e) and dominance (C) indices.Further analysis done using multivariate analysis was presented as 2D-ordination by Nonmetric Multi-Dimensional Scaling (NMDS). The composition of macrobenthic assemblages was dominated by gastropods (18 species), bivalves (9 species) and Polychaeta (7 species). Based on NMDS ordination, there was a tendency of grouping stations by sampling time. It is particularly so between sampling times II and III, and between sampling times I and III. However, this grouping did not occur between sampling times I and II. It may indicate that the macrobenthic assemblages were influenced by certain annual seasons.Meanwhile, depending on sampling locations, the assemblages were influenced by environmental variability. The stations were grouped by the aquacultural areas and reference area on the ordination with some overlapping stations positioned among them. However, the tendency of grouping the stations between IMTA and monocultural sites did not occur, implying both farming practices have a relatively similar impact on the structure of macrobenthic assemblages.