The condition of Myall Broadwater, and to some extent Myall Lake, is strongly influenced by runoff from the Myall River catchment. Dry conditions meant that there was little runoff during sampling, resulting in clear waters and small amounts of algae. The grade for Myall Broadwater has risen back to the good condition that was evident prior to 2017. The marked variability in condition, swinging from good to poor and back again, emphasises the need to continue to control nutrients from the catchment of the upper Myall River. Myall Lake has dropped slightly from excellent to good condition.
Grades for Wallis Lake continue to range from good to excellent, with excellent water clarity and only occasional undesirable growth of algae. The Mid Wallamba estuary continues to show consistent higher than desired growth of algae but this year saw an improvement in water clarity. Despite this, there was a slight decrease in seagrass range. Upstream parts of Wallamba Cove continue to be affected by runoff from Tuncurry stimulating algal growth. The Mid Coolongolook estuary continued to show a large amount of algal growth but generally acceptable water clarity. The storm runoff in March 2018 stimulated a large algal bloom in the Coolongolook. Other than in the Wallamba River, seagrass depth ranges did not change markedly from last year and ranged from poor in Wallamba River to good at Pipers and Wallis and excellent in Charlotte Bay.
The Karuah River and The Branch estuary continue to show signs of impaired estuary health with higher than desired algal growth in both locations. The algal score for The Branch was the highest recorded for any site this summer, highlighting the need to reduce nutrients within the catchment. Water clarity in the Karuah Estuary was excellent and good in The Branch. Unusually there was no seagrass in the mid to upper reaches of the Karuah River estuary which may be a consequence of past conditions.
The Khappinghat estuary, located in Saltwater National Park, is surrounded by Khappinghat Nature Reserve and is typically in excellent ecological condition. Algal growth was low but there was a slightly poorer than expected water clarity leading to a drop in score from excellent to good.
The Manning River estuary has maintained its good overall ecological condition. Water clarity was excellent throughout the river. It continues to have algal levels that are much greater than desired, particularly in the upper reaches. The high algal levels recorded are most likely due to perfect growing conditions throughout most of the sampling period. Clear warm water and abundant sunlight allow the algae to fully utilise nutrient runoff from the Catchment. Seagrass is an important component of the River’s biodiversity. The depth range where seagrass is able to grow increased from last year’s low due to increased water clarity.
Sampling wasn’t undertaken in Smith’s Lake in 2018, however results from the 2017 report card showed excellent results. The hot dry summer in 2017 influenced the results, ensuring that water clarity was excellent at all times, but this also meant that algal growth was occasionally greater than desired. The weather also resulted in markedly high water temperatures.
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