Newland Nearshore Marine Biounit
2014 Aquatic Ecosystem Condition Report
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- Seagrass cover varied depending on wave energy. Habitats in sheltered environments typically had moderate cover of Posidonia spp., while in more open exposed areas habitats were comprised largely of unvegated sand with patches of seagrass, possibly Posidonia coriacae.
- In autumn, seagrasses had a moderate to dense cover of epiphytic algae.
- Rocky reef communities were dominated by dense brown canopy algae, with diverse red and green fine branching algal communities filling out the understory.
About the Biounit
The Newland Biounit is located in the Eyre bioregion and extends from Talia Caves located to the south of Venus Bay to Cape Finniss and includes Waldegrave Island. The biounit has a south-westerly orientation facing into the Great Australian Bight and experiences high wave energy along the exposed sections of the coast with the only sheltered area in the lee of Waldergrave Island.
The biounit has a diverse mix of habitats reflective of the different environments. Unvegetated sand dominates the open coast, while the sheltered bays consist of seagrass, particularly Posidonia spp.. Rocky reefs in this area are dominated by large brown alga Ecklonia radiata and Cystophora spp. and the red alga Osmundaria spp. and Haliptilon spp. occurring in shallower waters.
There are no townships or shack settlements in this biounit and the adjacent land use is primarily cereal and modified pasture crops. However a large proportion of the coast is the Lake Newland Conservation park which can act to buffer land based surface runoff. Given the very low rainfall of the area, surface water runoff from agricultural land is likely to be minimal.
The assessment of identified threats to the nearshore habitats predicts that the Newland Biounit is likely to be in Excellent.
In sheltered parts of the biounit, meadows of Posidonia spp. dominated. While diverse rocky reef communities were also found between Waldegrave Island and the mainland. In contrast the open coast was inhabited by largely unvegetated sand, with sparse and patchy Posidonia coriacae(?) seagrass present.
There were some indicators of elevated nutrients during autumn with moderate to dense seagrass epiphytes, elevated chlorophyll and available nutrients in the water.
The condition of habitats in waters between 2–15 m deep throughout the Newland biounit was assessed based on monitoring data collected during autumn and spring 2014. There are some areas within the biounit that are deeper than 15 m which are not included as a part of this assessment.
The isolation and exposure of this biounit resulted in only 3 sites assessed in autumn and spring of 2014. The waters were relatively high energy, even in the shelter provided by Waldegrave Island. This low number of sites has been taken into consideration in the assessment.
In the shelter of Waldegrave Island, the sandy substrate was comprised of moderate cover of Posidonia spp. seagrass (eg: m0419) while any rocky substrate was covered with the robust brown canopy alga Ecklonia radiata and Cystophora spp.. Diverse red (including Plocamium spp.) and green (including Caulerpa spp.) coarse branching algal communities filled out the understory leaving very little exposed rock.
In contrast Colton (m0420) is located along the more exposed section of the biounit and was dominated by sand with sparse patchy Posidonia coriacae(?) which is likely to reflect the higher wave energy and dynamic sand environment.
In autumn the seagrass was typically covered in moderate to dense epiphytic algae, particularly at Colton (m0420). The water chemistry showed higher dissolved and total nutrients available at all sites and elevated phytoplankton at Waldegrave Island (m0419) during autumn. This pattern was not repeated in spring. Newland is commonly affected by upwellings which transport cool nutrient rich water from the continental shelf into coastal waters during autumn, which greatly contribute to the regional productivity and may help to explain the evelated nutrients seen here.
This assessment indicates that Newland is likely to be in Very Good condition suggesting that there may be some detectable changes compared to the natural state but these are unlikely to lead to affecting the way the ecosystem functions. This score may be a reflection of the small number of sites in this rapid assessment program and the current limited understanding of seagrass systems (eg: Posidonia coriacea communities) in higher energy environments.
The findings presented here are explained more thoroughly in the Eyre & Murat Assessment Report.
Pressures and management responses
|Agricultural runoff may transport nutrients through surface or groundwater into the nearshore environment during large rainfall events||Low agricultural activity currently within the surrounding land of Venus Bay and Port Kenny reduce the likelihood of this pressure.|