Kelp
Climate Change Daily Environment Repost

Hot ocean waters affecting New Zealand kelp

Kelp thrives in cold, nutrient-rich waters. It is one of the largest marine plants found in the earth’s oceans, and it is native to the cold waters off the coast of New Zealand, where it forms the foundation of local ecosystems. 

Divers have explored the kelp forest for years, and aboriginal culture embraces the bounty that comes from kelp ecosystems. The kelp is disappearing, however, as warmer oceans impinge on the New Zealand coastline.

Kelp thrives in the shallow waters and intertidal zones of exposed coastlines. These plants underpin the coastal ecosystem and provide a foundation for local biodiversity. Commercially important species like lobsters and abalone depend on the kelp forest habitats.  Since kelp survives in a limited temperature range, warming oceans have led to the degradation and disappearance of the kelp in many places along the coasts of both New Zealand and Tasmania.

Heat kills

The heat is coming in two forms. The first is a slow baseline warming trend for the Indian and Pacific oceans. Between 1950 and 2009, the respective rises in mean sea-surface temperatures of these two oceans were 0.65°C, and 0.31°C. The second factor is shorter-term increases in seawater temperatures, referred to as heatwaves. Because the kelp thrives in very shallow waters, these heatwaves incorporate both atmospheric and oceanic temperature rises. This means that the heat effects can be very localized.

Research on heatwaves shows that while they are historically common on the New Zealand coast, the duration and intensity of these events has increased since 2014. Over the summers of 2017 and 2018, the heat waves were particularly intense. The thermal surges were two times stronger than anything recorded since 1980. These heatwaves resulted in the elimination of bull kelp on over 60% of the reefs under study.

The 2019-2020 summer season in New Zealand may offer no respite. In December, satellites detected a massive ocean hot spot off the east coast of the country. This super-heated mass of water covers over one million square kilometers (the size of Texas) and has water temperatures as high as 5°C above average.

Traditional cycles disrupted

Gradual warming, and increasing occurrences of extreme weather conditions, are not unique to New Zealand, but they are currently taking a toll there. Species loss is a global problem, and the loss of anchor species, like kelp, in local ecosystems is another facet of a changing environment. 

To the west of New Zealand in Tasmania, the assessment for kelp ecosystems is bleak. In recent government inquiries, Dr. Neville Barrett from the Institute of Marine and Antarctic Studies commented that kelp forests are at a thermal tipping point. The continued exposure of the Tasmanian coast to the warm, nutrient-poor East Australian current and a lack of rejuvenation from the Southern Ocean upwelling has put them in permanent decline. When asked what could be done about it, he replied, “There is nothing we can do … it’s just too late.”


ArcheanWeb:

Heat affects the ocean’s food chain (Source: ArcheanWeb) – https://archeanweb.com/2020/01/30/heat-affects-the-oceans-food-chain/ Also:


Sources:

Tasmanian kelp forests dying as water warms, dive operator Mick Baron says (Annah Fromberg – ABC News) – https://www.abc.net.au/news/2017-02-21/tasmanian-kelp-forests-dying-as-water-warms-dive-operator-says/8289300 Also:

Local Extinction of Bull Kelp (Durvillaea spp.) Due to a Marine Heatwave (Front. Mar. Sci., 06 March 2019 | https://doi.org/10.3389/fmars.2019.00084 ) – https://www.frontiersin.org/articles/10.3389/fmars.2019.00084/full Also:

Massive ocean hot spot is the size of Texas (CNN) – https://www.cnn.com/videos/weather/2019/12/28/new-zealand-ocean-water-hot-spot-van-dam-nr-vpx.cnn Also:

Feature Photo: Kelp Forest Blue (NOAA) – This image is in the public domain because it contains materials that originally came from the U.S. National Oceanic and Atmospheric Administration, taken or made as part of an employee’s official duties. (Modified)

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.