Benthic Landscape Research Articles

Characterizing the microbiomes of Antarctic sponges: a functional metagenomic approach

Relatively little is known about the role of sponge microbiomes in the Antarctic marine environment, where sponges may dominate the benthic landscape. Specifically, we understand little about how taxonomic and functional diversity contributes to the symbiotic lifestyle and aids in nutrient cycling. Here we use functional metagenomics to investigate the community composition and metabolic potential of microbiomes from two abundant Antarctic sponges, Leucetta antarctica and Myxilla sp. Genomic and taxonomic analyses show that both sponges harbor a distinct microbial community with high fungal abundance, which differs from the surrounding seawater. Functional analyses reveal both sponge-associated microbial communities are enriched in functions related to the symbiotic lifestyle (e.g., CRISPR system, Eukaryotic-like proteins, and transposases), and in functions important for nutrient cycling. Both sponge microbiomes possessed genes necessary to perform processes important to nitrogen cycling (i.e., ammonia oxidation, nitrite oxidation, and denitrification), and carbon fixation. The latter indicates that Antarctic sponge microorganisms prefer light-independent pathways for CO2 fixation mediated by chemoautotrophic microorganisms. Together, these results show how the unique metabolic potential of two Antarctic sponge microbiomes help these sponge holobionts survive in these inhospitable environments, and contribute to major nutrient cycles of these ecosystems.

Assessing key ecosystem functions through soundscapes: A new perspective from coral reefs

Abstract The functioning of tropical coral reefs is imperilled by climate change, overfishing, and decreasing water quality. Maintaining their capacity to provide goods and services will critically depend on our ability to monitor their functioning at appropriate spatial and temporal scales. Given the constraints of traditional methods to respond to those needs, the potential of complementary tools such as Passive Acoustic Monitoring (PAM) is emerging. Coral reef soundscapes (i.e. ambient sound) encompass sounds produced by numerous organisms. Soundscape characteristics quantified by ecoacoustic indices have been found to reflect general ecosystem properties, such as diversity and abundance of fishes, and coral cover. The present study tested, on the virtually pristine coral reefs around Europa Island, South-West Indian Ocean, the capacity of acoustic indices to assess key ecosystem functions. Soundscapes were recorded during 2 h, and ecosystem functions were evaluated using video footage of the fish assemblages and underwater photogrammetry of the benthic landscapes. We found significant and strong correlations between six ecoacoustic indices and six key ecosystem functions, including habitat features and fish assemblage characteristics. The six ecoacoustic indices were representative of several combinations of frequency, amplitude and time analysis domains, highlighting the diversity of the functional information conveyed by soundscapes. Our findings reveal that a 2 h daytime recording on a coral reef could provide sufficient acoustic information to characterise major ecosystem functions of a site. This should facilitate the detection of functional disturbances at temporal and spatial scales adapted to the rapidity of upcoming climate changes. Our results also highlight the potential of ecoacoustics to bring novel and relevant insights in the functioning of ecosystems.

Using Underwater Imagery as a Complementary Tool for Benthos Sampling in an Area with High-Energy Hydrodynamic Conditions

Using Underwater Imagery as a Complementary Tool for Benthos Sampling in an Area with High- Energy Hydrodynamic Conditions Underwater imagery is increasingly being used in the description of communities and habitats, as a tool to aid in the designation and management of marine protected areas. Here, we developed an underwater imagery system to monitor the seafloor and benthic communities in the Raz Blanchard (Aldernez Race), an area in the English Channel characterized by high-energy hydrodynamics. Despite the difficult conditions of acquisition, the underwater images highlighted the heterogeneous nature of the seabed in the Raz Blanchard. In this way, underwater imagery is a useful tool in providing additional information to standard benthic observations, particularly for the description of sessile epifauna and benthic landscapes. This system is flexible, robust and simple enough to be used in coastal and offshore areas, and is suitable as a complementary tool in benthic surveys to monitor the status and changing trends of seabed fauna and could be applied in future surveys.

Habitat selection by green turtles in a spatially heterogeneous benthic landscape in Dry Tortugas National Park, Florida

We examined habitat selection by green turtles Chelonia mydas at Dry Tortugas National Park, Florida, USA. We tracked 15 turtles (6 females and 9 males) using platform trans- mitter terminals (PTTs); 13 of these turtles were equipped with additional acoustic transmitters. Location data by PTTs comprised periods of 40 to 226 d in varying months from 2009 to 2012. Core areas were concentrated in shallow water (mean bathymetry depth of 7.7 m) with a comparably dense coverage of seagrass; however, the utilization distribution overlap index indicated a low degree of habitat sharing. The probability of detecting a turtle on an acoustic receiver was inversely associated with the distance from the receiver to turtle capture sites and was lower in shallower water. The estimated daily detection probability of a single turtle at a given acoustic sta- tion throughout the acoustic array was small (<0.1 in any year), and that of multiple turtle detec- tions was even smaller. However, the conditional probability of multiple turtle detections, given at least one turtle de tection at a receiver, was much higher despite the small number of tagged tur- tles in each year (n = 1 to 5). Also, multiple detections of different turtles at a receiver frequently occurred within a few minutes (40%, or 164 of 415, occurred within 1 min). Our numerical esti- mates of core area overlap, co-occupancy probabilities, and habitat characterization for green turtles could be used to guide conservation of the area to sustain the population of this species.

The attenuation of current‐ and wave‐driven flow within submerged multispecific vegetative canopies

AbstractHistorically, submerged vegetative canopies have either been reported as or modeled after unispecific examples—communities comprised of only a single vegetative species or element type. Field surveys of a shallow Florida Bay seagrass meadow highlighted a more diverse benthic landscape. Although dominated by Thalassia testudinum, the communities were distinctly multispecific, composed of a mixture of both plant and algal species. Strap‐like seagrass elements defined the upper portion of these canopies (the upperstory) while broad‐bodied algal species were found concentrated close to the bed (the understory). To predict the hydrodynamic implications of this dual‐story canopy structure, we derived a new canopy flow attenuation model, formulated to account for vertical canopy heterogeneities like those seen at our field site. The model was validated through a series of laboratory experiments: multispecific canopy mimics were installed in a current‐wave flume and exposed to a range of unidirectional and oscillatory flows. Mean and fluctuating velocity was measured above and within each canopy to determine vegetation‐induced flow attenuation. Velocities near the bed were markedly reduced through the addition of understory elements, results that were consistent with model predictions. These findings suggest that accurate prediction of flow‐regulated processes like sediment transport and propagule dissemination depends on a thorough accounting of community composition. These properties are also expected to change in response to seasonal variability and episodic environmental stresses.

Benthic habitat β-diversity modeling and landscape metrics for the selection of priority conservation areas using a systematic approach: Magdalena Bay, Mexico, as a case study

Albeit the need and importance of protected areas worldwide, there is no best practice methodology for their placement and design as this depends on several factors such as resource availability, data disponibility, and technical capacity. In this study, we show a novel approach on the use of β-diversity modeling and landscape metrics for the selection of priority conservation areas to assist the management of Magdalena Bay, one of the most important bays of Mexico. Quantitative estimates on the percentage of cover of benthic substrates from 60 ground truthed sites were used to perform a cluster analysis using the Bray–Curtis similarity index. Seven habitats were recognized, with habitats characterized by an inter-mix of sand, seagrass, macroalgae and rock substrates. A thematic map of benthic habitats was produced utilizing a supervised classification with the maximum likelihood rule on a natural color mosaic of high resolution satellite scenes (overall accuracy 80%, Kappa = 0.69). Matlab was used to calculate β-diversity values based on the nature and distribution of habitats. A weighted overlay analysis considering habitat type, patch area/perimeter2 ratio and β-diversity was performed to prioritize areas for conservation. Three areas, which constitute ∼20% of the shallow benthic landscape, are proposed to be considered within a Marine Protected Area scheme. By selecting sites with these landscape characteristics we developed a cost-effective systematic approach to protect the natural processes responsible for maintaining diversity and the livelihoods of the local communities.

Spatial and Temporal Patterns in Macrofaunal Diversity Components Relative to Sea Floor Landscape Structure

We examined temporal changes in macrofaunal α- and β-diversity over several spatial scales (within patches, among patches, across landscapes and across regions) in Long Island Sound on the northeast USA coast. Regional ε-diversity was estimated at 144 taxa, however γ-diversity fluctuated over time as did α- and β-diversity components. Based on additive partitioning, patch- and region-scale β-diversity components generally had the highest contributions to γ-diversity; lower percentages were found at within-patch and landscape scales. Multiplicative diversity partitioning indicated highest species turnover at within- and among patch scales. For all partition results, within-patch and patch-scale β-diversity increased sharply when hypoxia impacted benthic communities. Spatial variation in diversity components can be attributed to the collection of different patch types at varying spatial scales and their associated habitats across the benthic landscapes, as well as gradients in depth and other estuarine-scale characteristics. Temporal variation in diversity components across spatial scales may be related to seasonal changes in habitat heterogeneity, species population dynamics, and seasonal disturbances. Rare species were significant and temporally consistent components of macrofaunal diversity patterns over different spatial scales. Our findings agree with other marine and terrestrial studies that show diversity components vary significantly over different spatial scales and the importance of habitat/landscape heterogeneity in supporting diversity. However, our results indicate that the relative contributions of scale-specific β-diversity components can also change significantly over time. Thus, studies of diversity patterns across patches and landscapes based on data collected at one time, or assembled into a single data set from different times, may not capture the full suite of diversity patterns that occur over varying spatial scales and any time-specific determinants of those patterns. Many factors that shape and maintain sedimentary communities vary temporally, and appear to play an important role in determining and maintaining macrofaunal diversity over different spatial scales.

Connections between hydrodynamics, benthic landscape and associated fauna in the Balearic Islands, western Mediterranean

Linking the abiotic and biotic traits of ecosystems is a critical step towards understanding their structure and functioning. Here we attempt to determine the connections between the hydrodynamics, benthic landscape and the associated fish communities on the coastal continental shelf off the Balearic Islands (western Mediterranean). Specifically we investigate the role the hydrodynamics play in shaping the benthic landscape, and whether the hydrodynamics affect the composition and structure of demersal fish communities. A realistic numerical model was used to establish the hydrodynamic characteristics of the area. The study area showed high hydrodynamic variability on a medium spatial scale (tens of km) in terms of mean water velocity ( Ū). Principal component analysis was used to determine the main gradients of macro-epibenthic variability. Redundancy analysis (RDA) was used to model the effect of the hydrodynamics on macro-epibenthic species. RDA was also used to model the effect of the hydrodynamics and macro-epibenthos on the abundance of the associated fish fauna, and on its biomass at a community level using biomass spectra classes. The results showed that the hydrodynamics had a significant influence on the distribution of both macro-epibenthic species and the associated fish species. The latter was also influenced by the macro-epibenthos. Fish size appeared to be a key attribute for the distribution of species across gradients of Ū and macro-epibenthic change. Our findings can be applied in ecosystem-based fisheries management, as they show that it is necessary to take into account both the biotic and abiotic traits of the habitats when the habitat use and requirements of the associated species are defined.

Macrobenthic biodiversity and sea floor landscape structure

Ascertaining the patterns and determinants of soft-sediment biodiversity is critical to our overall understanding of coastal and marine processes. Studies of diversity in the deep sea and neritic waters have largely focused on levels of species diversity, differences in these levels along depth and geographic gradients, and how environmental characteristics within and among different geographic areas may drive the differences and patterns found. Among the environmental characteristics examined, habitat structure and heterogeneity have been identified as potentially playing a key role they play in shaping biodiversity patterns. Although habitat-related factors such as sediment characteristics have always been considered, it has been in the absence of any quantified benthic landscape framework. A benthic landscape, or benthoscape, is comprised of a set of patches that are repeated over a kilometers -wide area. Such patches have within-patch structure and in soft-sediments are often defined by their geophysical characteristics, although distinct biotic patches also can comprise a benthoscape. Benthoscapes contain the habitats that generate and support soft-sediment species diversity, and these habitats indeed are a component of overall biodiversity. Although, the study of benthoscape structure and dynamics is only now emerging, marrying this with research on biodiversity patterns will move our understanding of both forward. A landscape framework would provide a quantitative spatial context for analyses of biodiversity at multiple scales and can help resolve how habitat heterogeneity and structure affect biodiversity in soft-sediment environments. Such information may substantively help in sea floor management and conservation.

Challenges in marine, soft-sediment benthoscape ecology

In this paper I address three sets of challenges that face ecologists who are studying soft-sediment benthic landscapes (or benthoscapes). These include (a) development of technology and analytical approaches for sea floor mapping and quantifying benthoscape structure, (b) development of benthoscape ecology theory that integrates ideas from terrestrial and other marine systems, but focuses on the unique aspects of these environments, and (c) making empirical headway. Coordinated efforts in all three areas are needed to make progress in understanding soft-sediment systems, which arguably comprise the largest set of landscapes on the earth. In particular, much more work is needed in relating biotic patterns to the actual spatial structural aspects of soft-sediment benthoscapes.

Currents, landscape structure, and recruitment success along a passive–active dispersal gradient

There exists a gradient in dispersal behavior from passive to active, which reflects organisms’ dependence upon currents vs. self-propelled movement. We asked: Do currents modify organism–landscape interactions to influence recruitment success along this dispersal gradient? Using a spatially-explicit cellular model, we simulated the recruitment success of three generalized dispersal strategies (walkers, swimmers, and drifters) through hierarchically structured benthic landscapes. We evaluated the relative recruitment success (recruited population size, overall area occupied, time to recruit) of the three dispersal strategies in similar landscapes, as well as the consequences of varying the total proportion of habitat suitable for recruitment, and the scale and pattern of habitat patchiness on recruitment success. In the presence of currents, swimmers and drifters generally recruited over larger areas and in less time than walkers. Differences among the dispersal strategies’ recruitment success were most pronounced when an intermediate number of good habitat cells (16–48% of landscape) were broadly dispersed across the landscape. Although recruitment success always increased with increasing proportion of good habitat, drifters were more sensitive, and swimmers less sensitive, to these landscape changes than walkers. We also found that organisms dispersing within currents typically responded non-linearly (logarithmically or exponentially) to increasing proportion of total good habitat, whereas walkers more often responded linearly.

Characterizing the role benthos plays in large coastal seas and estuaries: A modular approach

Ecologists studying coastal and estuarine benthic communities have long taken a macroecological view, by relating benthic community patterns to environmental factors across several spatial scales. Although many general ecological patterns have been established, often a significant amount of the spatial and temporal variation in soft-sediment communities within and among systems remains unexplained. Here we propose a framework that may aid in unraveling the complex influence of environmental factors associated with the different components of coastal systems (i.e. the terrestrial and benthic landscapes, and the hydrological seascape) on benthic communities, and use this information to assess the role played by benthos in coastal ecosystems. A primary component of the approach is the recognition of system modules (e.g. marshes, dendritic systems, tidal rivers, enclosed basins, open bays, lagoons). The modules may differentially interact with key forcing functions (e.g. temperature, salinity, currents) that influence system processes and in turn benthic responses and functions. Modules may also constrain benthic characteristics and related processes within certain ecological boundaries and help explain their overall spatio-temporal variation. We present an example of how benthic community characteristics are related to the modular structure of 14 coastal seas and estuaries, and show that benthic functional group composition is significantly related to the modular structure of these systems. We also propose a framework for exploring the role of benthic communities in coastal systems using this modular approach and offer predictions of how benthic communities may vary depending on the modular composition and characteristics of a coastal system.

Movement behaviour and dynamics of an aquatic insect in a stream benthic landscape

Understanding not just where organisms move but how they move is an important step towards integrating animal behaviour into landscape ecology. The three-dimensional landscape of a streambed provides an ideal setting for forging this integration because of the persuasive effects of flowing water. In this study, we experimentally examine the larval movement of the case-building caddisfly Agapetus boulderensis Milne, 1936 in response to two current velocities in each of five levels of contrasting habitat types (i.e., smooth patches that facilitate movement and thick algal patches that constrain movement). Detailed behavioural observations showed that larvae employed two distinctly different strategies of movement in different current velocities: faster crawling and slower pivoting. Our results suggest that individual decision-making between crawling and pivoting is related to the magnitude of current velocity across the streambed, and the frequency at which larvae employ these behaviours translates into differential movement rates and directions. Strong concordance between a conceptual model and our results supports the notion that the presence of structural "nonhabitat" patches at high current velocities may create areas of local flow interruption and refugia. This, in turn, plays an important role in eliciting either crawling or pivoting and in shaping patterns and directions of larval movement, and by extension resource acquisition.

Multi-scale Data Used to Analyze the Spatial Distribution of French Grunts, Haemulon Flavolineatum, Relative to Hard and Soft Bottom in a Benthic Landscape

We evaluated the day-time distribution of juvenile and adult French grunts, Haemulon flavolineatum, relative to the spatial configuration of hard and soft bottom areas in a benthic landscape. Probability of juvenile presence on hard bottom sites was inversely correlated with distance to soft bottom. Adults presence at hard bottom sites showed no significant relationship with distance to soft bottom. A significant and positive relationship was found between presence of juveniles on hard bottom sites and area of soft bottom within 100 m, but no significant relationship was found for area of soft bottom within 500 m. Adults exhibited no significant relationship with area of soft bottom for either distance tested. These distributions are suspected to be the result of the combined influence of larval settlement patterns and foraging behaviors associated with hard and soft bottom. This study indicates that data collected at very fine scales can be analyzed in the context of the broad-scale mosaic of habitats in the benthic landscape to predict patterns of fish distribution. Such spatially explicit conclusions are not possible through analysis of fine-scale or broad-scale data alone.

Identification of patch structure within marine benthic landscapes using a remotely operated vehicle

The spatial scale of megafaunal assemblage variation in apparently homogeneous subtidal sediment was investigated using quantitative observations from a remotely operated vehicle (ROV). Quantitative abundance estimates of surface-dwelling megafauna and biotic sediment features associated with burrowing megafauna were derived from video images using the Automated Benthic Image-Scaling System (ABISS), a novel method of applying scale to images collected by ROVs. Spatially referenced images were collected with a maximum sample separation of 400 m within a broader area of apparently homogeneous sediment in Plymouth Sound (Devon, UK) during May 2000 and March 2001. Rank-correlograms were constructed to examine the extent and form of the megafaunal spatial structure. The megafaunal assemblage was neither uniformly distributed nor temporally stable. A hierarchy of spatial structure was detected within the megafaunal assemblage, whereby patches with minimum radius between 123 and 163 m were nested within patches up to 400-m radius. The approach described in this paper offers ways forward to address how variation of megafaunal spatial structure affects macrofaunal assemblage structure and to discuss the application of remote imaging to map and predict the conservation value of subtidal soft sediments.

Paleocommunity and evolutionary ecology of Paleozoic crinoids

Crinoids were a common component of Paleozoic benthic paleocommunities, yet they have been under-utilized in paleoecological analyses. Recent efforts to incorporate disarticulated ossicles into these analyses have greatly increased the robustness of paleoecological patterns noted for the Crinoidea. Analyses of crinoid functional morphology, particularly filtration dynamics, have provided testable hypotheses concerning the distribution of crinoids among benthic environments. These models predict that crinoids with dense-mesh filtration fans should be most common in high energy, shoreward paleoenvironments, whereas open-fan crinoids should be most common in low-energy, offshore paleoenvironments. Review of the Paleozoic fossil record appears to support these general predictions—from the Late Ordovician to the end of the Paleozoic, dense-fan crinoids are most abundant in nearshore paleoenvironments, whereas open-fan crinoids are most abundant offshore.The partitioning of crinoid diversity through the Paleozoic shifted through time. Beta diversity was highest in the Ordovician, implying that the early diversification of crinoids was focused on partitioning the benthic landscape among taxa. Beta diversity was quite low by the late Paleozoic, however, local and within-habitat alpha diversity was much greater than during the Ordovician. This resulted in generally higher levels of eurytopy in the late Paleozoic compared to the Ordovician. Patterns of faunal disassembly associated with regional extinctions in North America during the Ordovician and Permian underscore the differences in the paleoecology of these crinoid faunas.

Food relations between coexisting native Hawaiian stream fishes

In this study, an ecomorphological perspective is used to examine the role of feeding morphology in shaping patterns of food resource use and coexistence for Awaous guamensis and Sicyopterus stimpsoni, two native gobies (Gobiidae) which inhabit mountainous streams of the high Hawaiian Islands. Using data from underwater census, gut content analysis, and benthic sampling, I determined that A. guamensis, the generalist, had nearly unchallenged use of invertebrate foods. Overlap in fitness for algal use, however, resulted in a partitioning of benthic algae, with A. guamensis having domain over most green algae (43.0% of diet), whereas S. stimpsoni the algal specialist, fed predominantly on blue-green algae (22.6% of diet) and diatoms (54.2% of diet). Cladophora sp. (Chlorophyta) and pennate diatoms (Chrysophyta) were determined to be the ‘primary algal foods’ of A. guamensis and S. stimpsoni, respectively, and were utilized in a mutually exclusive manner with other ‘secondary algal foods’ depending upon availability. Heterogeneity, found in the abundance and composition of algal and invertebrate foods in the benthic landscape both spatially and seasonally, may be regulated by stream flow and periodic disturbance. This changing mosaic of foods is suggested as having provided opportunities for minimizing competitive conflicts and enhancing the potential for stream species to coexist. Competition for preferred foods, created by inter-specific overlap in ecomorphology and spurred by constraints placed on food diversity by the extreme geographic isolation of the Hawaiian Islands, is hypothesized as having played an evolutionary role in shaping resource use patterns which facilitate coexistence.