Large variations in eutrophication among estuaries reflect massive differences in composition and biomass of macroalgal drift

• Published in: Marine pollution bulletin 2021-06, Vol.167, p.112330, Article 112330
• Main Authors: Potter, Ian C., Rose, Thomas H., Huisman, John M., Hall, Norman G., Denham, Ainslie, Tweedley, James R.
• Format: Article
• Language: English
• Subjects: Agricultural land; Algae; Anthropogenic changes; Anthropogenic factors; Biomass; Brackishwater environment; Climate change; Drift; Dry weight; Estuaries; Estuarine dynamics; Estuarine environments; Eutrophic rivers; Eutrophication; Human influences; Microtidal estuaries; Mineral nutrients; Nutrients; Opportunistic chlorophytes; Prevalence; Salinity; Seasonal growth; Seaweeds; South-western Australia; Waterfowl
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2021.112330

The characteristics of detached macroalgae (drift) in nearby highly eutrophic and mesotrophic estuaries in south-western Australia are compared to elucidate the magnitude and types of changes that occur in macroalgal drift when estuaries receive excessive nutrient input. Drift characteristics in the large basins of the microtidal, eutrophic Peel-Harvey and mesotrophic Swan-Canning, which is not subjected to large nutrient inputs directly from agricultural land, differed markedly. Biomass (dry weight) in mesotrophic estuary was dominated by rhodophytes (92%), particularly Laurencia and Hypnea, and in eutrophic estuary by opportunistic chlorophytes (68%), especially Chaetomorpha and Ulva. Prevalence and biomass of drift were far greater in the eutrophic estuary, particularly during summer and autumn when macroalgal growth rose sharply. Macroalgal biomass in the eutrophic estuary was positively related to salinity. These results facilitate predictions of how climatic and other anthropogenic changes influence extent of macroalgal growth and thus change the estuarine environment. •Macrophyte drift in nearby microtidal mesotrophic and eutrophic estuaries compared•Rhodophytes dominant in mesotrophic estuary and chlorophytes in eutrophic estuary•Biomass 23 times greater in eutrophic estuary, due to high summer and autumn values•Drift prevalence and dry weight in both estuaries increased from winter to autumn•Biomass positively related to salinity in both mesotrophic and eutrophic estuaries