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PhD candidate, University of Peradeniya

PINBOARD SUMMARY

effect of connection between coral reefs, mangroves and seagrasses on fishes

Utilization of different habitats varies between juvenile and adult fishes. Understanding this interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas (MPAs). Fishes move daily among different habitats for feeding or shelter, all habitats being used may be equally important, regardless of scale and type; therefore, each of these habitats must be included in the establishment of MPA boundaries. Even when establishing a MPA for biodiversity conservation, the inclusion of multiple habitats within a MPA could further enhance its effectiveness, as such a MPA may be able to protect not only habitat-specific species, but also those that inhabit multiple habitats. For these reasons, understanding the interconnectivity of reef fishes among different habitats is a key requirement for making effective management plans in coastal ecosystems, particularly for determining the component habitat structures in a MPA.Conservation strategies should therefore protect connected habitats and facilitate the natural migration of species among them. The first step in creating this is identifying the utilization and importance of specific habitats in the seascape. Connected and well-functioning nearshore marine habitats can support coastal resilience, food provisioning (through productive fisheries) and carbon sequestration. The overall objective of this research will be to elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats using baited Remote Underwater Video surveys at four sites in Sri Lanka.This study will determine the importance of connectivity of habitats with regard to differences in community structure and spatial distribution of fish, based on the density distribution of juveniles and adults.

6 ITEMS PINNED

Contemporary connectivity is sustained by wind- and current-driven seed dispersal among seagrass meadows.

Abstract: Seagrasses are clonal marine plants that form important biotic habitats in many tropical and temperate coastal ecosystems. While there is a reasonable understanding of the dynamics of asexual (vegetative) growth in seagrasses, sexual reproduction and the dispersal pathways of the seeds remain poorly studied. Here we address the potential for a predominantly clonal seagrass, P. australis, to disperse over long distances by movement of floating fruit via wind and surface currents within the coastal waters of Perth, Western Australia. We first simulated the dominant atmospheric and ocean forcing conditions that are known to disperse these seagrass seeds using a three-dimensional numerical ocean circulation model. Field observations obtained at 8 sites across the study area were used to validate the model performance over ~2 months in summer when buoyant P. australis fruit are released into the water column. P. australis fruit dispersal trajectories were then quantified throughout the region by incorporating key physical properties of the fruit within the transport model. The time taken for the floating fruit to release their seed (dehiscence) was incorporated into the model based on laboratory measurements, and was used to predict the settlement probability distributions across the model domain.The results revealed that high rates of local and regional demographic connectivity among P. australis meadows are achieved via contemporary seed dispersal. Dispersal of seeds via floating fruit has the potential to regularly connect meadows at distances of 10s of kilometres (50% of seeds produced) and infrequently for meadows at distances 100 s km (3% of seeds produced).The spatial patterns of seed dispersal were heavily influenced by atmospheric and oceanographic conditions, which generally drove a northward pattern of connectivity on a regional scale, but with geographical barriers influencing finer-scale connectivity pathways at some locations. Such levels of seed dispersal infer greater levels of ecological and genetic connectivity and suggest that seagrasses are not just strongly clonal.

Pub.: 22 Apr '15, Pinned: 12 Apr '18

Effects of ocean sprawl on ecological connectivity: impacts and solutions

Abstract: The growing number of artificial structures in estuarine, coastal and marine environments is causing “ocean sprawl”. Artificial structures do not only modify marine and coastal ecosystems at the sites of their placement, but may also produce larger-scale impacts through their alteration of ecological connectivity - the movement of organisms, materials and energy between habitat units within seascapes. Despite the growing awareness of the capacity of ocean sprawl to influence ecological connectivity, we lack a comprehensive understanding of how artificial structures modify ecological connectivity in near- and off-shore environments, and when and where their effects on connectivity are greatest. We review the mechanisms by which ocean sprawl may modify ecological connectivity, including trophic connectivity associated with the flow of nutrients and resources. We also review demonstrated, inferred and likely ecological impacts of such changes to connectivity, at scales from genes to ecosystems, and potential strategies of management for mitigating these effects. Ocean sprawl may alter connectivity by: (1) creating barriers to the movement of some organisms and resources - by adding physical barriers or by modifying and fragmenting habitats; (2) introducing new structural material that acts as a conduit for the movement of other organisms or resources across the landscape; and (3) altering trophic connectivity. Changes to connectivity may, in turn, influence the genetic structure and size of populations, the distribution of species, and community structure and ecological functioning. Two main approaches to the assessment of ecological connectivity have been taken: (1) measurement of structural connectivity - the configuration of the landscape and habitat patches and their dynamics; and (2) measurement of functional connectivity - the response of organisms or particles to the landscape. Our review reveals the paucity of studies directly addressing the effects of artificial structures on ecological connectivity in the marine environment, particularly at large spatial and temporal scales. With the ongoing development of estuarine and marine environments, there is a pressing need for additional studies that quantify the effects of ocean sprawl on ecological connectivity. Understanding the mechanisms by which structures modify connectivity is essential if marine spatial planning and eco-engineering are to be effectively utilised to minimise impacts.

Pub.: 13 Feb '17, Pinned: 12 Apr '18

Diversity of corals and benthic algae across the shallow-water reefs of Andaman Islands: managing the valuable ecosystems

Abstract: Abstract The Andaman Islands characterize one of the relatively unexplored coral reef zones of the Indian subcontinent. A few benthic biodiversity studies have been carried out to date, but several coral and algal species still remain to be evaluated in terms of their abundance, vigour and conservation priority. In absence of a comprehensive, reliable dataset, inter-relationships between anthropogenic impacts and climate alterations with the coral reefs cannot be assessed authentically. This paper addresses the coupled themes of biodiversity and reef management in the Andaman Islands by examining the percentage cover of corals and benthic algae from shallow-water ecosystems across the coasts of Havelock, Neil, Ross, Jolly Buoy Islands and Chidiyatapu beach proximal to Port Blair. Four major reef types were observed: coral-dominated, algae-dominated, neutral setting and algae overgrowing dead reefs. Jolly Buoy Island had the highest percentage cover of scleractinian corals and crustose coralline algae. Turf algae were most abundant at the Ross Island, while other macroalgae showed highest abundance at Chidiyatapu. Overall species diversity values for corals and algae were highest at the Jolly Buoy and Chidiyatapu, respectively. Given that corals and algae are critical reef components, management paradigms must consider the abundance and frequency of both these biogenic entities in the seascape. The needs, expectations and objectives of the people dependent on coral reef ecosystems also need to be considered. Long-term monitoring is imperative in understanding the natural typology of reefs and managing the possible algal encroachments. Refined management efforts that include greater thrust on development of marine protected areas and reserves; establishment of connectivity between various coral ecosystems of the region; control of invasive algae; and increasing awareness among the local people as well as tourists will ensure continued support of ecosystem to maintain healthy reefs. Collectively, the results are used to promote some strategies to conserve the Andaman coral reefs and cope with the detrimental anthropogenic and climate changes in these coastal habitats.AbstractThe Andaman Islands characterize one of the relatively unexplored coral reef zones of the Indian subcontinent. A few benthic biodiversity studies have been carried out to date, but several coral and algal species still remain to be evaluated in terms of their abundance, vigour and conservation priority. In absence of a comprehensive, reliable dataset, inter-relationships between anthropogenic impacts and climate alterations with the coral reefs cannot be assessed authentically. This paper addresses the coupled themes of biodiversity and reef management in the Andaman Islands by examining the percentage cover of corals and benthic algae from shallow-water ecosystems across the coasts of Havelock, Neil, Ross, Jolly Buoy Islands and Chidiyatapu beach proximal to Port Blair. Four major reef types were observed: coral-dominated, algae-dominated, neutral setting and algae overgrowing dead reefs. Jolly Buoy Island had the highest percentage cover of scleractinian corals and crustose coralline algae. Turf algae were most abundant at the Ross Island, while other macroalgae showed highest abundance at Chidiyatapu. Overall species diversity values for corals and algae were highest at the Jolly Buoy and Chidiyatapu, respectively. Given that corals and algae are critical reef components, management paradigms must consider the abundance and frequency of both these biogenic entities in the seascape. The needs, expectations and objectives of the people dependent on coral reef ecosystems also need to be considered. Long-term monitoring is imperative in understanding the natural typology of reefs and managing the possible algal encroachments. Refined management efforts that include greater thrust on development of marine protected areas and reserves; establishment of connectivity between various coral ecosystems of the region; control of invasive algae; and increasing awareness among the local people as well as tourists will ensure continued support of ecosystem to maintain healthy reefs. Collectively, the results are used to promote some strategies to conserve the Andaman coral reefs and cope with the detrimental anthropogenic and climate changes in these coastal habitats.

Pub.: 01 Dec '16, Pinned: 12 Apr '18

Linking oceanographic processes and marine resources in the western Caribbean Sea Large Marine Ecosystem Subarea

Abstract: The western Caribbean, a subarea of the Caribbean Sea Large Marine Ecosystem, includes the Mesoamerican Barrier Reef System, the Yucatan Basin, the Cayman Basin and the Yucatan Channel. Here we discuss the main oceanographic features of the western Caribbean Sea and present some examples of marine resources distributed throughout the western Caribbean Sea LME subarea along different spatial scales. Particular attention is given to their planktonic stages when physical oceanographic features (such as eddies and gyres, or current systems) can operate either as forces that promote larval dispersal or as barriers enhancing larval retention, as this determines their connectivity. Bluefin tuna, the early life stages (eggs and larvae) of reef fish, the Caribbean Spiny lobster, and the Queen conch are presented as examples. Dispersal distances depend on the oceanographic phenomena, with larger dispersals expected where intense currents occur, such as in the Yucatan Current. Conversely, retention can be expected in the presence of gyres such as the Honduras Gyre and Yucatan Basin eddies. There is a growing body of evidence supporting the need for a multi-scale approach in order to understand the complexity of LMEs. Moreover, the connectivity between regions in the western Caribbean Sea LME subarea, as shown by the exchange of marine resources and physical oceanographic processes, requires an international policy that supports collaborative efforts to monitor the dynamics of coastal and oceanic habitats together with marine resources.

Pub.: 24 Jan '17, Pinned: 12 Apr '18