Standard Presentation Australian Marine Sciences Association 2026 Conference

Freshwater flowing into the sea is not wasted - Integrating land-sea connectivity into the Protection and Management of Marine Transitional Waters (139341)

Lara van Niekerk 1 , Susan S Taljaard 1 , Stephen J Lamberth 2 , Steven P Weerts 1
  1. Council for Scientific and Industrial Research, South Africa, Rosebank, WESTERN CAPE, South Africa
  2. Branch: Fisheries Research, Department of Forestry, Fisheries and the Environment (DFFE), South Africa, Cape Town, Western Cape, South Africa

Globally, 36 000km3 of freshwater, 18 billion tonnes of sediment and 4 billion tons of dissolved material enter coastal regions annually. Changes in freshwater flow influence land-sea connectivity, impacting sediment supply, salinity, turbidity, nutrients and organics; affecting biodiversity and ecosystem services, e.g. 77% of total fishery harvest linked to freshwater flow (Milliman and Farnsworth 2013; Broadley et al. 2022).

Weak protection of land-sea connectivity in coastal ecosystems is as much a policy gap as it is a scientific challenge. While many countries promote policies that manage and protect freshwater-dependent ecosystems, most legislation falls short of providing for freshwater to the coast beyond that allocated to estuaries (van Niekerk et al. 2019). Few countries have developed explicit marine environmental flow (E-flow) methods as part of formal allocation processes. The assumption perpetuated is that, having taken care of estuaries, adjacent coastlines would receive sufficient sediment, nutrients, and organic matter to sustain critical ecosystems and associated services.

However, ensuring land-sea connectivity requires an explicit evaluation of marine E-flow requirements, supported by strong policy and implementation frameworks that can assure a fair distribution of freshwater flows and their benefits from Source-to-Sea. South Africa has embarked on a process of delineating, classifying, and formally protecting these unique marine ecosystems, but has made less progress in ensuring the essential freshwater flows that facilitate land-sea connectivity and support these ecosystems.

  1. Broadley AJM, Stewart-Koster B, Burford MA and Brown. C. 2022. A global review of the critical link between river flows and productivity in marine fisheries. 32(3): 805–825. doi:https://doi.org/10.1007/s11160-022-09711-0.
  2. Milliman JD and Farnsworth KL. 2013. River discharge to the coastal ocean: a global synthesis. Cambridge University Press, UK. https:// doi. org/ 10. 1017/ CBO97 80511 781247
  3. Van Niekerk L, Taljaard S, Janine JB, Lamberth SJ, Huizinga P, Jane JK and Wooldridge TH. 2019. An environmental flow determination method for integrating multiple-scale ecohydrological and complex ecosystem processes in estuaries. Science of the Total Environment 656: 482–494.