World Ocean Day 2025: Get to know South Australia’s oceans and why they matter!

Sun­day (June 8) is World Ocean Day, an oppor­tu­ni­ty to unite, cel­e­brate and advo­cate for our oceans and a healthy climate.

South Aus­tralians know the val­ue of our oceans. Our coast­line sus­tains our state in so many ways — from the annu­al migra­tion of whales calv­ing in the Great Aus­tralian Bight, to a thriv­ing fish­ing indus­try famous for world-class abalone and cray­fish. Our pris­tine beach­es attract thou­sands of locals and tourists who enjoy surf­ing, swim­ming, div­ing and fishing.

A healthy, thriv­ing ocean ben­e­fits us all. Sad­ly, since March, a nat­u­ral­ly occur­ring, harm­ful algal bloom has affect­ed parts of South Australia’s coastline.

The bloom has caused dis­coloured water and foam along parts of Fleurieu Penin­su­la, Kan­ga­roo Island and the south­ern coast of Yorke Peninsula. 

It has affect­ed var­i­ous marine wildlife, includ­ing fish, sharks, rays, sea­hors­es and oth­er gilled species, with dead marine life wash­ing up on beaches.

Experts believe there are 3 plau­si­ble con­tribut­ing fac­tors caus­ing the bloom:

• A marine heat­wave that start­ed in Sep­tem­ber 2024 – with sea tem­per­a­tures about 2.5°C warmer than usu­al – com­bined with calm con­di­tions, light winds and small swells.
• The 2022 – 23 Riv­er Mur­ray flood wash­ing extra nutri­ents into the sea.
• An unprece­dent­ed cold-water upwelling in sum­mer 2023 – 24 that has brought nutri­ent-rich water to the surface.

Gov­ern­ment agen­cies con­tin­ue to mon­i­tor the situation. 

The impacts of the algal bloom fur­ther high­light the impor­tance of our oceans and their role in sus­tain­ing life as we know it. 

Get to know South Australia’s ocean 

1. We don’t have one ocean but 3: The South­ern, Indi­an and Pacif­ic Ocean all meet and inter­mix off south­ern Aus­tralia, cre­at­ing a dynam­ic envi­ron­ment that influ­ences every aspect of our lives from the weath­er we expe­ri­ence, to the coastal envi­ron­ment we enjoy and the food we eat.
2. Warm water inputs: In the west­ern por­tion of South Australia’s ocean waters, tem­per­a­tures are influ­enced by a warm water cur­rent from West­ern Aus­tralia called the Leeuwin Cur­rent. These warm cur­rents allow some high­ly mobile fish species, typ­i­cal­ly of trop­i­cal ori­gin, to be observed in the Great Aus­tralian Bight.
3. Cold water inputs: The Great South Aus­tralian Coastal Upwelling Sys­tem is respon­si­ble for bring­ing nutri­ent-rich cold water to the sur­face, cre­at­ing phy­to­plank­ton blooms and pro­vid­ing key food sources for krill and sar­dines, which are, in turn, impor­tant food sources for whales and fish such as tuna.
4. Sig­nif­i­cant car­bon sink: The South­ern Ocean is a major car­bon sink, absorb­ing more car­bon diox­ide than it emits. This helps mit­i­gate the effects of cli­mate change by reduc­ing the amount of CO2 in the atmosphere.
5. Great South­ern Reef: The Great South­ern Reef stretch­es from WA to NSW and sup­ports amaz­ing marine bio­di­ver­si­ty, much of which is found nowhere else on the plan­et. SA’s ocean­ic waters help sup­ply nutri­ents, oxy­gen and food to the GSR, where you can find blue grop­ers, leafy see drag­ons, giant cut­tle­fish and a host of sharks and ray species. There is also an incred­i­ble vari­ety of life grow­ing on the GSR, includ­ing macroal­gae, sponges, crus­taceans, bry­ozoans, echin­o­derms and molluscs.
6. Marine parks: South Aus­tralian waters are pro­tect­ed by a net­work of 19 marine parks in state waters, and 7 Aus­tralian marine parks in Com­mon­wealth waters. Marine parks are an impor­tant tool for con­serv­ing marine biodiversity.

Why are oceans important?

1. Cli­mate reg­u­la­tion: The ocean absorbs approx­i­mate­ly 30% of car­bon emis­sions and gen­er­ates more than half the planet’s oxy­gen, help­ing com­bat cli­mate change.
2. Food source: It pro­vides 15% of the ani­mal pro­tein con­sumed glob­al­ly, essen­tial for many populations.
3. Jobs and liveli­hoods: 3 bil­lion peo­ple depend on the ocean for their livelihoods.
4. Eco­nom­ic devel­op­ment: The ocean econ­o­my is esti­mat­ed to be worth tril­lions of dol­lars, dri­ving sig­nif­i­cant eco­nom­ic growth.
5. Sur­vival: A healthy ocean is cru­cial for our over­all well­be­ing and survival.

Why do oceans need to be saved?

Our oceans face sig­nif­i­cant threats due to a com­bi­na­tion of human activ­i­ties and envi­ron­men­tal changes.

• Pol­lu­tion, par­tic­u­lar­ly plas­tic waste, is con­t­a­m­i­nat­ing marine ecosys­tems and harm­ing wildlife. It’s esti­mat­ed that 8 mil­lion met­ric tonnes of plas­tic enter the oceans annu­al­ly, lead­ing to dead­ly con­se­quences for marine ani­mals that ingest or become entan­gled in it.
• Over­fish­ing is deplet­ing fish pop­u­la­tions faster than they can replen­ish, dis­rupt­ing the bal­ance of marine ecosys­tems and threat­en­ing food secu­ri­ty for mil­lions who depend on seafood as a pri­ma­ry pro­tein source.
• Cli­mate change is caus­ing ocean tem­per­a­tures to rise and sea lev­els to increase, which con­tributes to coral bleach­ing and the loss of vital coastal habitats.
• Addi­tion­al­ly, the oceans are absorb­ing about 30% of the car­bon diox­ide emit­ted by human activ­i­ties, lead­ing to ocean acid­i­fi­ca­tion that affects shell-form­ing species and the broad­er marine food web.

These com­bined fac­tors high­light the urgent need for glob­al con­ser­va­tion efforts to pro­tect our oceans and ensure their health for future generations.

How can I help pro­tect our oceans?

To help pro­tect our ocean, you can:

1. Reduce plas­tic use: Use reusable bags, bot­tles and straws to keep plas­tic out of the ocean.
2. Get involved in restora­tion: Get involved with restora­tion projects aimed at restor­ing ecosys­tems, such as man­groves for coastal pro­tec­tion or sea­grass for car­bon seques­tra­tion, help­ing to reduce ocean acid­i­fi­ca­tion. Check out your local coun­cil ini­tia­tives to get involved or explore the Depart­ment for Envi­ron­ment and Water’s vol­un­teer­ing options.
3. Clean up: Join beach or riv­er clean-up events to remove rub­bish from waterways.
4. Save water: Use less water to reduce runoff that can car­ry pol­lu­tion to the ocean.
5. Learn and share: Edu­cate your­self about marine life and share what you learn with friends and fam­i­ly to raise aware­ness. Join a snorkelling tour or become a cit­i­zen sci­en­tist.

For updates on South Australia’s algal bloom, vis­it the Depart­ment for Envi­ron­ment and Water’s web­site.

Look­ing for more? Dis­cov­er how bio­di­ver­si­ty helps address cli­mate change.