Marine health is one of three conceptual models that broadly focus on the biophysical systems in our region. They describe the ‘health’ of the systems and should be considered in association with the socially based conceptual models socially based conceptual models and subregional information to get a full picture of what we know about our region.
View the marine health model.
About marine health
Marine waters are a significant part of the region, making up approximately 41% of its total area. Most of the region’s marine waters are in Gulf St Vincent, with the boundary extending to the south into Backstairs Passage and the more exposed waters of the eastern Fleurieu Peninsula. The region also includes parts of two marine parks; Encounter and Upper Gulf St Vincent.
Marine biodiversity in Gulf St Vincent is typical of cool temperate biota but includes significant levels of uniqueness for many algae, fish and marine invertebrates.
The gulf has extensive seagrass meadows, mangroves and samphire or saltmarsh, as well as significant sandy and soft bottomed habitats and reef areas.
The seagrass meadows along the metropolitan coast are mostly Posidonia and Amphibolis communities. Outside the metropolitan areas, coastal seagrass meadows appear to be relatively healthy with continuous and extensive dense seagrass still in Encounter Bay.
The region’s subtidal temperate reefs are dominated by large seaweeds or macroalage and invertebrates such as sponges, bryozoans, ascidians, hydroids, echinoderms, molluscs and crustaceans. Structure and species composition is related to wave action and other physical influences. Below the brown algal canopy are a number of understoreys, comprising smaller green, brown or red algae.
A healthy marine environment supports a substantial commercial and recreational fishing industry, and provides a nursery habitat for resident and migratory species.
Near-shore marine waters are exposed to a range of external pressures that can cause their condition to decline. These include short-term pulse inputs such as stormwater through to constant discharges such as those from sewage treatment plants. Both near shore and off shore habitats can also be impacted by a range of marine based activities such as dredging.
A case study: Protecting South Australia’s valuable seagrass communities
This case study identifies the value of seagrass to the environment and to the community.
Metropolitan Adelaide seagrass shows the results of many years of impacts from the urban environment, in sharp comparison to the good condition of seagrass on the Fleurieu Peninsula. The causes of seagrass loss along the metropolitan coast are well known and this knowledge should be used to ensure the same impacts do not occur along the Fleurieu Peninsula.