Diversity Of Benthic Assemblages Research Articles

Thermal regime, together with lateral connectivity, control aquatic invertebrate composition in river floodplains

Abstract Large river floodplains are dynamic environments, where alternating low and high flows are key ecological processes shaping aquatic biota. As a result of fluctuations in flow in floodplain channels, the diversity of benthic assemblages is assumed to result from the balance between surface flow connections, which are dominant during high flows, and groundwater inputs, which are dominant during low flows. However, the relative importance of these inputs in explaining aquatic invertebrate diversity has never been tested. The response of aquatic invertebrates to hydrological changes of a river floodplain was investigated in seven braided and six braided–anastomosed floodplain channels of the French upper Rhône River that are fed by three different processes: groundwater supply (which controls the thermal inertia of the water bodies), surface slow flow connections (i.e. diffuse overbank flows; passive overflow), and surface shear stress‐related connections (i.e. condensed flows; active overflow) during high flows. Generalised dissimilarity models indicated that floodplain invertebrate composition had complex relationships with the three processes considered. The relative importance of the latter appeared dependent upon the morphology of the floodplain channels. In the braided channels, the effects of shear stress‐related connections were more prominent than in the anastomosed ones, for which the effects of the three processes were more similar. Overall, the diversity of flow connections, that is, lateral surface water connections (both shear stress‐related and slow, as defined above) and vertical connection with groundwater (inferred through thermal inertia) enhanced the species turnover at the reach scale. Thermal inertia influenced invertebrate composition when, during low flow periods, surface flow connections had limited effect. Our results highlighted that the role of hydrologic connectivity upon floodplain diversity cannot be reduced to a single process. They also indicate the importance of vertical connectivity for maintaining biodiversity in floodplain habitats where surface flow connectivity is neither frequent nor constant.

Diversity and time-series analyses of Caribbean deep-sea coral and sponge assemblages on the tropical island slope of Isla de Roat\xe1n, Honduras

Shore-based submersible operations, from 2006 to 2020, have allowed us to examine megabenthic assemblages along the island margin of Isla de Roatán from depths of about 150 to 750 m, including repeated observations of the same organisms. These dives were used to photo-document a diverse benthic assemblage and observe the health and condition of the sessile fauna in a well-explored but relatively undocumented area of the Mesoamerican Reef. Samples were collected by dip net, and some dives profiled the water column chemistry in the year 2011. The deep-sea coral assemblage observed off Roatan exhibits high abundance and diversity. The sessile habitat-forming taxa consist primarily of at least 20 different octocorals (e.g., Plexauridae, Primnoidae, Coralliidae, Isididae, and Ellisellidae) and 20 different sponges each (Demospongiae and Hexactinellida), with several known and unknown taxa of Zoantharia, Antipatharia (Bathypathes spp), and Scleractinia (e.g., Desmophyllum pertusum, Dendrophyllia alternata, Madracis myriaster, and solitary taxa). Crinoidea were also abundant and diverse, represented by at least nine species. Epifaunal assemblages associated with corals include at least 24 macroinvertebrate species dominated by Asteroschema laeve (Ophiuroidea) and Chirostylus spp. (Decapoda: Anomura). Repeated observations of a few large octocoral colonies over many years illustrate patterns of predation, recolonization, and epibiont host fidelity, including a 14-year record of decline in a plexaurid octocoral (putatively Paramuricea sp.) and loss of its resident ophiuroids. The shore-based submersible provides a practical and relatively inexpensive platform from which to study coral and sponge assemblages on a deep tropical island slope. The deep-sea coral gardens are likely to harbor new species and new discoveries if more samples can be acquired and made available for taxonomic research.

Intra-Annual Variation in Mesophotic Benthic Assemblages on the Insular Slope of Southwest Puerto Rico as a Function of Depth and Geomorphology

There is limited information on the intra-annual variability of mesophotic coral ecosystems (MCEs), worldwide. The benthic communities, measured as % cover, of two geomorphologically different mesophotic sites (El Hoyo and Hole-in-the-Wall) were examined during 2009–2010 in southwest Puerto Rico. Depths sampled were 50 and 70 m. At each site/depth combination, two permanent transects, measuring 10-m long by 40-cm wide, were surveyed by successive photoquadrants, 0.24 m2 in area. Scleractinian corals, octocorals, macroalgae, crustose coralline algae (CCA), sponges and unconsolidated sediment were the main components along the transects. Significant community differences were observed both among sites and among depths. Differences among sites were greater at 50 m than at 70 m. The El Hoyo site at 50 m was the most divergent, and this was due to a lower coral and sponge cover and a higher algal cover (Amphiroa spp., Peyssonnelia iridescens, turf) relative to the other site/depth combinations. As a consequence, the differences in community structure with depth were larger at El Hoyo than at Hole-in-the-Wall. The communities at 70 m were distinguished from those at 50 m by the greater proportion of the corals Agaricia undata, Madracis pharensis and CCA, and a reduced cover of the cyanobacterium Schizothrix. Temporal variation in the benthic assemblages was documented throughout the year. For both mesophotic sites, the magnitude of change at 50 m was significantly greater than at 70 m. For both depths, the magnitude of change at El Hoyo was significantly greater than at Hole-in-the-Wall. All assemblages experienced almost the same temporal patterns, despite the differences in species composition across sites and depths. Changes in temporal patterns are driven by an increase in the percent cover of the macroalgae Dictyota spp., and a decrease in the percent cover of non-colonized substrata (sand, pavement or rubble). Relatively rapid, intra-annual changes are dictated by the negative correlation between cyclic Dictyota spp. cover and open substrata cover. Other observed mechanisms for rapid community changes in the photoquadrants were diseases and collapses of substrata along with their associated fauna indicating that small-scale disturbance processes may play an important role within MCEs.

Disease Outbreak in a Keystone Grazer Population Brings Hope to the Recovery of Macroalgal Forests in a Barren Dominated Island

Macroalgal forests play a key role in shallow temperate rocky reefs worldwide, supporting communities with high productivity and providing several ecosystem services. Sea urchin grazing has been increasingly influencing spatial and temporal variation in algae distributions and it has become the main cause for the loss of these habitats in many coastal areas, causing a phase shift from macroalgae habitats to barren grounds. The low productive barrens often establish as alternative stable states and only a major reduction in sea urchin density can trigger the recovery of macroalgal forests. The present study aims to assess if the 2018 disease outbreak, responsible for a strong reduction in the sea urchinDiadema africanumdensities in Madeira Island, was able to trigger a reverse shift from barren grounds into macroalgae-dominated state. By assessing the diversity and abundance of benthic sessile organisms, macroinvertebrates and fishes before, during and after that particular mass mortality event, we evaluate changes in benthic assemblages and relate them to variations in grazer and herbivore densities. Our results revealed a clear shift from barren state to a macroalgae habitat, with barrens characterized by bare substrate, sessile invertebrate and Crustose Coralline Algae (CCA) disappearing after the mortality event. Overall variations in benthic assemblages was best explained by four taxa (among grazers and herbivores species). However, it was the 2018 demise ofD. africanumand its density reduction that most contributed to the reverse shift from a long stable barren state to a richer benthic assemblage with higher abundance of macroalgae. Despite this recent increase in macroalgae dominated habitats, their stability and persistence in Madeira Island is fragile, since it was triggered by an unpredictable disease outbreak and depends on howD. africanumpopulations will recover. With no control mechanisms, local urchin populations can easily reach the tipping point needed to promote a new shift into barren states. New conservation measures and active restoration are likely required to maintain and promote the local stability of macroalgal forests.

A series of ecostratigraphic events across the Langhian/Serravallian boundary in an epicontinental setting: the northern Pannonian Basin

The SO-1 core situated in the NE part of the Pannonian Basin represents a parastratotype of the Badenian stage (regional Central Paratethys stage corresponding to the Langhian and Serravallian). A 150-m-thick succession was deposited between ~ 14.2 and 13.5 Ma (dated by the last common occurrence of Helicosphaera waltrans to the last occurrence of Sphenolithus heteromorphus) and spans the Langhian/Serravallian boundary. The section was subdivided into four units: (1) A transgressive carbonate–siliciclastic complex (core depth ~ 150–122 m) deposited in an inner to mid carbonate ramp setting. Carbonate deposition was episodically interrupted by the input of terrigenous phytodetritus as a result of increased precipitation. (2) Tuffaceous siltstone (core depth ~ 122–48 m) corresponding to a sea-level highstand. This unit starts with a Pteropoda immigration event (14.5–14.2 Ma), which could be related to the closing of the Indian-Mediterranean corridor that triggered a change from Indian- to Atlantic-controlled surface circulation in the Mediterranean-Paratethys basin system. An enhanced proportion of high-nutrient markers and a decreased abundance of warm-water plankton might be indicative of eutrophication and cooling of Paratethyan waters at this time. (3) Lowstand sandstone (core depth ~ 48–26 m) indicating stabilization of sea-grass meadows with eutrophic and hypoxic conditions within their root system. A sea-level fall at this time is correlated with the Ser 1 event. (4) A Serravallian transgressive event (core depth ~ 26–5 m) associated with an increase in diversity of benthic assemblages and stabilization of stenohaline assemblages.

Benthic studies in LTER sites: the use of taxonomy surrogates in the detection of long-term changes in lagoonal benthic assemblages

In benthic studies, the identification of organisms at the species level is known to be the best source for ecological and biological information even if time-consuming and expensive. However, taxonomic sufficiency (TS) has been proposed as a short-cut method for quantifying changes in biological assemblages in environmental monitoring. In this paper, we set out to determine whether and how the taxonomic complexity of a benthic assemblage influences the results of TS at two different long-term ecological research (LTER) sites in the Po delta region (north-eastern Italy). Specifically, we investigated whether TS can be used to detect natural and human-driven patterns of variation in benthic assemblages from lagoonal soft bottoms. The first benthic dataset was collected from 1996 to 2015 in a “choked” lagoon, the Valli di Comacchio, a lagoon characterised by long water residence times and heavy eutrophication, while the second was collected from 2004 to 2010 in a “leaky” lagoon, the Sacca di Goro, a coastal area with human pressure limited to aquaculture. Univariate and multivariate statistical analyses were used to assess differences in the taxonomic structure of benthic assemblages and to test TS on the two different datasets. TS seemed to work from species to family level at both sites, despite a higher natural variability of environmental conditions combined with multiple anthropogenic stressors. Therefore, TS at the family level may represent effective taxonomic surrogates across a range of environmental contexts in lagoon environments. Since the structure of the community and the magnitude of changes could influence the efficiency of taxonomic surrogates and data transformations in long-term monitoring, we also suggest periodic analyses at finer taxonomic levels in order to check the efficiency of the application of taxonomic substitutes in routine monitoring programmes in lagoon systems.

Spatial variability in reef-fish assemblages in shallow and upper mesophotic coral ecosystems in the Philippines.

The variability in reef-fish species assemblages was examined at three geographic locations in the Philippines (Apo, Abra and Patn), each showing varying levels of disturbances (low to high) at two depths, shallow-water reef (SWR; 8-20 m) and the upper mesophotic coral ecosystem (MCE; 30-35 m). Fish species assemblages varied among locations and between depths. Differences in fish assemblages among locations corresponded to the variability in benthic assemblages and levels of disturbances, wherein locations with higher coral cover and less disturbances had the highest fish species richness, abundance and biomass. Variation in fish assemblages between depths was also associated with changes in benthic assemblages and possibly inaccessibility to local fishing techniques. Fish species richness decreased with depth in all locations, but biomass increased only in the MCEs of Apo and Abra, which is a similar pattern exhibited in many MCEs. Our results suggest that despite location differences, depth had a relatively consistent influence on fish species assemblages, particularly in locations exposed to low and intermediate disturbance. Under high disturbance, MCEs exhibit similar vulnerability to SWRs.

Time-dependent effects of orientation, heterogeneity and composition determines benthic biological community recruitment patterns on subtidal artificial structures

Worldwide, coastlines are becoming increasingly hardened by infrastructure in response to population growth, need for space, and coastal protection. Coastal and marine infrastructure (CMI) supports fewer species and lower abundance and diversity than analogous natural rocky habitats, which can alter community composition and ecosystem functioning. Efforts to develop ecological engineering solutions that offset these negative consequences on biodiversity while retaining engineering function abound, but to date few studies have investigated the role of multiple factors simultaneously driving patterns of biotic colonisation. Here, the role of surface heterogeneity, chemical composition and surface orientation was evaluated over a 6-month period. An increase in habitat heterogeneity, the replacement of shale for ground oyster shell (cue) and downward orientation was predicted to increase species richness, diversity and abundance. Orientation and heterogeneity greatly affected species richness, abundance, and community composition, and the inclusion of ground oyster shell (cue) increased bivalve recruitment but had only a marginal effect on community structure. Community formation was facilitated by low light but inhibited by sedimentation. On upward-facing surfaces, sediment accumulation on high complexity surfaces expanded niche heterogeneity, and supported communities comprised of burrowing polychaetes and predatory species. Surface orientation and heterogeneity are key factors influencing larval recruitment, and in supporting diverse benthic assemblages on artificial structures. These factors should be considered during the design phase of new engineering projects if the negative consequences of artificial structures are to be minimised while ensuring engineering function is maintained.

Eco-engineering rock pools to a seawall in a tropical estuary: Microhabitat features and fine sediment accumulation

Seawalls made from rock and concrete are engineered to defend coastlines and infrastructure from sea level rise, storm surge and shoreline erosion. However, while they provide a poor substitute for natural intertidal habitat, emerging designs addressing this biodiversity deficit have incorporated eco-engineering concepts with promising results. This study tested whether adding inexpensive household flower boxes (artificial rock pools) to a seawall in a tropical region would support benthic flora and fauna, and whether simple orientation of boxes improves benthic assemblage colonization. Boxes were positioned at mean tide height (1.1 m AHD) along a seawall in tropical Townsville, Australia. Nine boxes were deployed: three positioned vertically on the seawall, while three positioned at 45° facing towards the sea, and three positioned at 45° facing towards the land. Tilting the artificial rock pools at 45° compared overhang walls (simulating rocky shoreline ledge microhabitat) to vertical walls of artificial rock pools. After 12mths, boxes had accumulated (particularly inside on overhang walls compared to outside walls) a greater surface cover of algae and invertebrates. After the second year, box inside walls supported vastly different assemblages compared to outside box walls regardless of orientation, with the most diverse benthic assemblage found on overhang walls, giving support to the conclusion that artificial rock pools on seawalls support more biodiversity (of native species, with no non-indigenous species found) from tilting and creating overhangs. The turbid nature of this coastal region contributed to sediment accumulation at about 25 mm/yr, regardless of box orientation, which may pose maintenance problems (and cost) for managers, and if unchecked could negate any advantages offered by these engineered pool features.

Benthic macrofaunal structure and secondary production in tropical estuaries on the Eastern Marine Ecoregion of Brazil.

Tropical estuaries are highly productive and support diverse benthic assemblages within mangroves and tidal flats habitats. Determining differences and similarities of benthic assemblages within estuarine habitats and between regional ecosystems may provide scientific support for management of those ecosystems. Here we studied three tropical estuaries in the Eastern Marine Ecoregion of Brazil to assess the spatial variability of benthic assemblages from vegetated (mangroves) and unvegetated (tidal flats) habitats. A nested sampling design was used to determine spatial scales of variability in benthic macrofaunal density, biomass and secondary production. Habitat differences in benthic assemblage composition were evident, with mangrove forests being dominated by annelids (Oligochaeta and Capitellidae) whereas peracarid crustaceans were also abundant on tidal flats. Macrofaunal biomass, density and secondary production also differed between habitats and among estuaries. Those differences were related both to the composition of benthic assemblages and to random spatial variability, underscoring the importance of hierarchical sampling in estuarine ecological studies. Given variable levels of human impacts and predicted climate change effects on tropical estuarine assemblages in Eastern Brazil, our data support the use of benthic secondary production to address long-term changes and improved management of estuaries in Eastern Brazil.

Unsustainable Land Use, Sediment-Laden Runoff, and Chronic Raw Sewage Offset the Benefits of Coral Reef Ecosystems in a No-Take Marine Protected Area

Unsustainable land uses may result in poor watershed management, increased soil erosion, poorly-planned urban development, increased runoff, and sewage pollution, creating an environmental stress gradient across coastal coral reefs. This study was aimed at: 1) Evaluating water quality within and outside the Canal Luis Peña Natural Reserve (CLPNR), Culebra Island, Puerto Rico; 2) Determining if there was any significant environmental stress gradient associated to land-based non-point source pollution; and 3) Characterizing shallow-water coral reef communities across the gradient. Strong gradient impacts associated to sediment-laden and nutrient-loaded runoff pulses, in combination with non-point raw sewage pulses, and sediment bedload, impacted coastal coral reefs. Water quality showed significant spatio-temporal fluctuations (p<0.0001), largely responding to heavy rainfall and subsequent runoff pulses. Benthic community structure showed significant spatial variation along the environmental stress gradient (p=0.0002). Macroalgae, dead coral surfaces, algal turf, and low coral species richness, species diversity index (H’c), and evenness (J’c) dominated benthic assemblages across reefs frequently impacted by runoff pulses and sediment bedload. The combination of fecal coliform and enterococci concentrations were correlated with variation in benthic community structure (Rho=0.668; p=0.0020). The combined variation in salinity, dissolved oxygen and enterococci concentrations explained 75% of the observed spatial variation in benthic assemblages (R2=0.7461; p=0.0400). Local human stressors affected coral reefs within no-take CLPNR and risk analyses suggest it may offset its ecological benefits. There is a need to design and implement integrated coastal-watershed management strategies to address multiple land use activities, including erosion-control best management practices, watershed reforestation, and sewage pollution control.

Early Maastrichtian benthos of the chalk at Kronsmoor, northern Germany: implications for Late Cretaceous environmental change

Lower Maastrichtian strata (Belemnella obtusa and lower–middle B elemnella sumensis cephalopod biozones) at the Saturn quarry near Kronsmoor (northern Germany) were logged and sampled in detail (33 bulk samples of about 6 kg each) for high-resolution quantitative palaeoecological analysis of the benthic fauna. Following standardised preparation, the size fractions 500 μm–1 mm and >1 mm were considered, documenting a diverse benthic assemblage of bryozoans, brachiopods, bivalves, various echinoid taxa, asteroids, ophiuroids, crinoids, sponges, small-sized sabellids and serpulids, cirripedes and foraminifera. A general, gradual up-section increase in the abundance of benthic faunas was recognised. Furthermore, from the lower to the upper part of the section, epifaunal suspension feeders became more dominant as the mobile guilds (epifaunal and shallow infaunal) saw a reduction in numbers. These observations parallel results obtained from low-resolution macrofossil analyses of this interval that documented an impoverished lower and a rich upper assemblage, the latter clearly dominated by epifaunal suspension feeders. Palaeoecological data of benthic community relicts at Kronsmoor are indicative of increased nutrient availability during the early Maastrichtian. However, in the absence of any evidence of increased productivity in the overlying photic zone (calcareous nannofossil data), a lateral input (upwelling) of nutrient-rich waters onto the shelf to fuel the benthic ecosystem has to be considered. This view is supported by records of contemporaneous changes in latest Cretaceous ocean circulation that followed the latest Campanian cooling event, inclusive of a southward spread of waters of intermediate depth from high latitudes.

Spatial patterns in the distribution of benthic assemblages across a large depth gradient in the Coral Sea, Australia

The Queensland Plateau in the Coral Sea off north-eastern Australia supports numerous submerged and emergent reefs. Osprey Reef is an emergent reef at the northern tip of the plateau ~1500 m in elevation. Over such a large depth gradient, a wide range of abiotic factors (e.g., light, temperature, substratum etc.) are likely to influence benthic zonation. Despite the importance of understanding the biodiversity of Australia’s Coral Sea, there is a lack of biological information on deep-water habitats below diving depths. Here, we used a deep-water ROV transect to capture video, still photos and live samples over a depth range spanning 92 to 787 m at North Horn on Osprey Reef. Video analysis, combined with bathymetry data, was used to identify the zones of geomorphology and the benthic assemblages along the depth gradient. There were marked changes in the geomorphology and the substrate along this depth gradient which likely influence the associated benthos. Cluster analysis indicated five benthic assemblage groups, which showed clear zonation patterns and were generally predictable based on the depth and sedimentary environment. These results are the first quantitative observations to such depths and confirm that the waters of the Coral Sea support diverse benthic assemblages, ranging from shallow-water coral reefs to mesophotic coral ecosystems, to deep-water azooxanthellate corals and sponge gardens. The knowledge provided by our study can inform management plans for the Coral Sea Commonwealth Marine Reserve that incorporate the deeper reef habitats and help to minimise future damage to these marine ecosystems.

Habitat-related patterns of soft-bottom macrofaunal assemblages in a brackish, low-diversity system (southern Baltic Sea)

Coastal areas provide a high variety of sedimentary habitats that influence the structure of resident fauna even on small geographical scales. Therefore, examinations of spatial variations in benthic assemblages require background knowledge of the environmental and biotic heterogeneity of habitats in order to understand ecological processes in such areas. The effect of habitat-related abiotic and biological variables on macrofaunal benthic assemblages was studied seasonally in 2010 and 2011 in the brackish, semi-enclosed Puck Lagoon (Gulf of Gdańsk, southern Baltic Sea). Based on macrophytal biomass, two discrete benthic regions were identified in the lagoon: a region of large biomass and a region of few macrophytes. The quality of the surface sediment organic matter (measured as C/Nsed ratio), depth, and benthic macrophyte composition accounted for within-region variation, which led to the identification of four habitats. Shallow sandy sediments with low C/Nsed ratios provide high quality sedimentary food for animals that, together with species-rich, dense macrophyte vegetation, support diverse assemblages. High C/Nsed ratios and peat outcrops in shallow sands exert a negative effect on macrofaunal diversity. Two deeper sandy habitats with less massive, species-poor vegetation tend to host distinct faunal assemblages of higher abundance and biomass. The importance of benthic vegetation for macrofaunal assemblages in the southern Baltic Sea is suggested to stem from its complex spatial structure that offers a number of microniches for infaunal and epifaunal species. The effect of macrophytes on benthic faunal assemblages was consistent throughout most of the year with the strongest influence in summer when macrophytes reached the highest biomass.

Marine communities on oil platforms in Gabon, West Africa: high biodiversity oases in a low biodiversity environment.

The marine biodiversity of Gabon, West Africa has not been well studied and is largely unknown. Our examination of marine communities associated with oil platforms in Gabon is the first scientific investigation of these structures and highlights the unique ecosystems associated with them. A number of species previously unknown to Gabonese waters were recorded during our surveys on these platforms. Clear distinctions in benthic communities were observed between older, larger platforms in the north and newer platforms to the south or closer to shore. The former were dominated by a solitary cup coral, Tubastraea sp., whereas the latter were dominated by the barnacle Megabalanus tintinnabulum, but with more diverse benthic assemblages compared to the northerly platforms. Previous work documented the presence of limited zooxanthellated scleractinian corals on natural rocky substrate in Gabon but none were recorded on platforms. Total estimated fish biomass on these platforms exceeded one ton at some locations and was dominated by barracuda (Sphyraena spp.), jacks (Carangids), and rainbow runner (Elagatis bipinnulata). Thirty-four percent of fish species observed on these platforms are new records for Gabon and 6% are new to tropical West Africa. Fish assemblages closely associated with platforms had distinct amphi-Atlantic affinities and platforms likely extend the distribution of these species into coastal West Africa. At least one potential invasive species, the snowflake coral (Carijoa riisei), was observed on the platforms. Oil platforms may act as stepping stones, increasing regional biodiversity and production but they may also be vectors for invasive species. Gabon is a world leader in terrestrial conservation with a network of protected areas covering >10% of the country. Oil exploration and biodiversity conservation currently co-exist in terrestrial and freshwater ecosystems in Gabon. Efforts to increase marine protection in Gabon may benefit by including oil platforms in the marine protected area design process.

INTEGRATED APPROACH TO ECOLOGICAL AND SOCIO-ECONOMIC RESEARCH TO SUPPORT THE OIL AND GAS INDUSTRY: THE GREAT AUSTRALIAN BIGHT COLLABORATIVE RESEARCH SCIENCE PROGRAM

ABSTRACT BP is investing $A1.43B and drilling four exploratory wells in the hope of discovering a new deep-water oil and gas province in the Great Australia Bight (GAB). The GAB is one of Australia's most valuable marine ecosystems. It supports globally significant populations of seabirds and marine mammals, diverse and endemic benthic assemblages and important fishing, aquaculture and ecotourism industries. Two research agencies (CSIRO, South Australian Research and Development Institute) and two universities (University of Adelaide, Flinders University of South Australia) recently entered into a collaborative research partnership with BP Australia to undertake an integrated study of the ecological processes and socio-economic importance of the GAB. Uniquely, this four year $20M research program is being undertaken during the exploration phase and conducted as a single integrated program. The Research Program is comprised of seven themes: physical oceanography; pelagic ecosystem and environmental drivers; benthic biodiversity; ecology of iconic and apex predators; petroleum geology and geochemistry; socio-economic values; and data integration and ecosystem modelling. Sixteen inter-related projects are being undertaken by some of Australia's leading marine scientists and will involve at least seven post-graduate Ph.D. students. Scientific quality assurance is provided by a review process that involves an Independent Science Panel and BP's international Subject Matter Experts. Ecological data collected during the study will be publically available. Findings will be presented to stakeholders and regulators and published in technical reports and scientific papers throughout the course of the program. The program is one of the few whole of system studies ever undertaken in Australia and is the first large-scale, integrated study of the ecosystems, resources and socio-economic values of the GAB. The approach has several advantages over undertaking discrete projects on key issues near the start of the production phase.1)BP Australia's financial contribution has leveraged significant investment from the other partners.2)Establishing baseline environmental conditions during the exploration phase provides the opportunity to conduct temporally replicated analyses of the ecosystem prior to commencement of production, should it occur.3)Engaging with the local scientific community builds on the existing knowledge base and working relationships with stakeholders and will assist the development of relevant local scientific capability.4)An integrated program provides for efficient development and validation of whole of system (i.e. ecological and socio-economic) models that elucidate interconnections among components of the system and can inform decisions regarding future development and predict, monitor and assess potential future impacts.

Idiosyncratic effects of protection in a remote marine reserve

A 10 yr study was carried out in the Tremiti Archipelago, a multiple-use Marine Protected Area (MPA) several miles off the mainland (South Adriatic, Italy), with a very small and isolated no-take area established in 1989 and characterized by limited enforcement. Patterns of variation in benthic assemblages along the intertidal rocky shores and in the rocky subtidal inside and outside the no-take area were examined between 2001 and 2010. Remarkable changes in the intertidal assemblages were detected within the no-take area, with an increase of Cystoseira canopies and the development of more diversified understory assemblages through time. Signs of regression in Cystoseira were documented in unprotected control areas. Conversely, <20 yr after the MPA designation, bare rock and patches of crustose coralline algae characterized subtidal assemblages in the no-take area. Increasing spatial heterogeneity of both intertidal and subtidal assemblages, probably representing an early warning of increasing human pressure, was also assessed. Data on primary production showed significantly higher values in the control areas than in the no-take area, with increasing values over time, indicating that the observed patterns are triggered by a combination of different drivers. Our results suggest that: (1) the effects of protection over benthic assemblages greatly depend on the habitats considered, which in turn, respond differently to specific human pressures occurring within and outside the reserve. A careful analysis of the distribution and intensity of all the activities allowed within multiple-use MPAs is critical for improving the effectiveness of conservation actions. (2) Isolation per se does not guarantee exclusion from human activities. In the presence of low enforcement, isolation may play a limited role in mitigating human pressures on benthic assemblages and may impair the connectivity of reserve networks.

Benthic survey of natural and artificial reefs off Mar del Plata, Argentina, southwestern Atlantic

This study describes the macrofaunal assemblages of subtidal rocky reefs off Mar del Plata in order to compare the macro invertebrate assemblages settled on shipwrecks with those of nearby reef sand to characterize the fish fauna associated with natural (NR) and artificial (AR) reefs. Topographic characterizations and surveys of invertebrates and fishes were performed in November and December 2005, using SCUBA diving. A non-parametric multivariate analysis was used to analyze the environmental and biological data. The reefs were mainly distinguished by their depth and the position of the substrate. The red calcareous algae, Corallina officinalis, dominated the shallowest NR, whereas conspicuous mytilid assemblages of Mytilus platensis were present at depths over 3 m, sea anemones, Anthothoe chilensis, were more abundant between 6 and 10 m, and the soft coral, Tripalea clavaria, was found at nearly 20 m depth. No differences were found between horizontal ARs and the adjacent NRs. The greatest differences were found between the communities of vertical and horizontal substrates, both in NRs and ARs. Fifteen fish species were recorded in the analyzed area. Species having strong site fidelity, e.g., Acanthistius brasilianus and Pseudopercis semifasciata, were clearly more abundant and/or frequent in ARs (shipwrecks) than in NRs. This pioneer study in the surveyed area showed that reef sallow the settlement of diverse benthic assemblages. ARs also provide refuge for fishes. As sport fishing and diving are activities being carried out in Mar del Plata, where tourism is one of the main economic resources, the protection of such areas should be considered in conservation plans.

Spatial variability in macroinvertebrate assemblages along and among neighbouring equatorial glacier-fed streams

1. During the past two decades, understanding of the structure and function of glacier-fed stream ecosystems at temperate latitudes has increased substantially. In contrast, information on their tropical counterparts is very limited. We studied three neighbouring glacier-fed streams in the tropical Andes of Ecuador. Our main goals were (i) to determine overall longitudinal patterns in density, taxon richness and the composition of macroinvertebrate assemblages and driving factors in equatorial glacial streams and (ii) to examine variability among replicate streams in faunal metrics and assemblages, and stream-specific effects of supposed environmental key factors. 2. We measured four geographical and 17 environmental factors and collected five Surber samples (500 cm2) of macroinvertebrates at each of nine sites, three sites along three streams. The streams were located 1–5 km apart. In each stream, the three sites were placed at comparable distances from the glacier and were grouped as ‘upper’ (50–200 m), ‘middle’ (1.5 km) and ‘lower’ sites (3.5–5.6 km). 3. In total, 2200 individuals (64% chironomids) were collected and 47 taxa (30 dipterans, 18 of these Chironomidae) identified. Density ranged from 176 to 372 ind. m−2, and the number of taxa ranged from 2 to 6 at the upper sites and 868–3044 ind. m−2 and 21–27 taxa at the lower sites. Density, number of taxa, rarefied richness and axis-1 coordinates from a MDS ordination increased logarithmically with distance from the glacier. These faunal metrics were equally related to altitude and glacier per cent of catchment and correlated with maximum conductivity, mean temperature, mean daily maximum temperature and a channel stability index. As expected, the mean difference in distance decay in similarity was higher at the upper (47% km−1) than at the lower reaches (20% km−1) of the streams. 4. The number of taxa varied among sites within the upper and middle groups, but not among the lower sites. In contrast, but in accordance with our expectation, assemblage composition did not differ among upper sites but did so at middle and lower sites, following a supposed decrease in environmental harshness along the streams. Relationships between faunal metrics and the four environmental variables mean temperature, the stability index, chlorophyll a and coarse particulate organic matter also varied among the three streams. Generalised linear model analyses revealed that temperature interacted with stream on macroinvertebrate density, while chlorophyll a had a significant effect on the number of taxa in interaction with stream and stability. 5. The basic predictions of the Milner et al. (2001a), model regarding longitudinal faunal patterns and temperature and stability as main driving factors were met by our three replicate equatorial glacial streams. Qualitative departures from the model were mainly because of zoogeographical differences. We demonstrated that variability in assemblages between comparable sites in closely situated streams was considerable, and the effect of key environmental factors varied among streams and interacted with other factors. Quantifying spatial variation in benthic assemblages may help us foresee possible consequences for biodiversity as a result of glacial retreat.

Effects of structural diversity and identity of patches of habitat on diversity of benthic assemblages

AbstractA fundamental problem in ecology, regardless of habitat or system, is understanding the relationship between habitats and assemblage of organisms. It is commonly accepted that differences in composition and surrounding landscape of habitats affect the diversity of assemblages, although there is not much empirical evidence because of difficulties of manipulating structure in many habitats. These relationships were examined experimentally, using habitats of artificial turfs that are colonized by diverse assemblages of gastropods. Each habitat was made of nine sub‐habitats, which were sampled individually to allow tests of hypotheses about the effect of type of habitat and the influence of other adjacent sub‐habitats on the colonizing assemblage. Turf habitats were deployed for 8 weeks on a rocky shore after which they were collected and the colonizing assemblages of gastropods sampled. Independently of the types of turfs combined to form different habitats, there were more species where there was more than one type of component in a habitat (i.e. structural diversity). The type of habitat (i.e. structural identity) itself had little or no influence on the colonizing assemblage. The number of species colonizing short‐sparse and short‐dense turfs was influenced by which type of habitat was adjacent. Thus, when units of one type (e.g. short‐sparse turf) were added to a patch of habitat of long‐sparse turfs, the number of species in short‐sparse turfs was greater than in patches of the same type. This also increased total number of taxa in the whole patch of habitat. These results show how diversity of gastropods colonizing heterogeneous patches of habitat is influenced not only by the number of types of sub‐habitats, but also by interactions with surrounding sub‐habitats. These findings reiterate the importance of investigating the role of structure of habitats and of their surrounding landscapes across different systems, irrespective of their size or associated assemblages of organisms.