An eco-narrative Kimberley Marine Park - North west marine region

This report is one in a series of eco-narrative documents that synthesise our existing knowledge of Australia’s individual Marine Parks. This series is a product of the National Environmental Science Program Marine Biodiversity Hub Project D1, which seeks to collate, synthesise and visualise biophysical data within the parks. These documents are intended to enable managers and practitioners to rapidly ascertain the ecological characteristics of each park, and to highlight knowledge gaps for future research focus.

Kimberley Marine Park is characterised by a gently sloping seabed comprising platforms and terraces, crossed by a series of valleys and channels that incise 20 – 50 m into the seabed. These valleys define the ancestral pathways of the larger rivers that drain to the modern Kimberley coast, and where mapped in high resolution preserve the form of coastal estuaries. Today, these rivers do not supply large volumes of sediment to the offshore, with sediments in the marine park dominated by relict marine carbonates. Areas of stable hardground are restricted to small, flat-topped banks that rise to several metres above surrounding seabed. The oceanographic regime of the park is characterised by strong tidal currents, with the additional dynamic of internal waves that set-up strong currents with the capacity to transport sand as bedload. Together, these hydrodynamic conditions produce relatively turbid conditions and fields of large bedforms up to 8 m high. The regional-scale Holloway Current that feeds warm, oligotrophic waters from the north also influences the oceanography of the park. As a result, the surface waters have relatively low primary productivity.

The marine fauna observed within the park include a range of megafauna, notably humpback whales, dugong and turtles. The latter include a variety of turtle species that nest on islands outside Kimberley Marine Park (e.g. Lacepede Islands), but which have been tracked moving through the park. Similar tracking of humpback whales provides evidence that the park overlaps their migration route. Information on demersal fish and sharks within the park is lacking and is based on regional studies that suggest a high degree of endemism among the offshore fish species. Evidence of climate change influence in the Kimberley offshore region is provided in the sea surface temperature record, which shows a clear warming trend that is slightly higher than the national average; coupled with the impact of marine heat waves.

The benthic biological communities within Kimberley Marine Park include sessile and infaunal communities that are broadly typical of tropical northern Australia, though our knowledge of these assemblages is limited to a small number of surveys in targeted areas (e.g. Lynher Bank in the south of the park). These surveys observed relatively sparse epifauna communities, but included a number of species of coral and sponge that were observed for the first time in the park. It is therefore likely that the diversity of corals and sponges remains underestimated. Further sampling of these benthic communities is therefore warranted.

The information in this eco-narrative forms an initial characterisation of Kimberley Marine Park.

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