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Satellites reveal coastal health of New Zealand

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For the first time, satellites have been used to track the health of coastal waters around Aotearoa New Zealand

In a new report commissioned by the Department of Conservation (DOC), NIWA analyzed satellite images to measure changes in suspended sediment — or total suspended solids (TSS) — in our coastal waters.

Dissolved solids contain a variety of substances, such as clay, silt, microalgae and their decomposing products. High concentrations of total dissolved solids can cause problems in estuaries, coasts, oceans, and aquatic life.

By looking at nearly 20 years of monthly satellite images of New Zealand’s coasts, scientists have found diverse trends in TSS over time across the country, with concentrations generally increasing around the South Island and decreasing concentrations around the North Island.

A higher total solids content can affect the ability of marine life, such as the baby blue penguin, to hunt food. It can also block light from reaching underwater plants and is associated with elevated levels of pathogens, nutrients, and pollutants.

DOC technical advisor Helen Kettles says that getting too much sediment into coastal waters is a serious threat to marine life.

“This research helps us understand coastal areas likely to benefit from improved conservation efforts and track how conditions have changed over time. It is good to learn more about how satellite monitoring of water clarity will be useful in the future,” Helen said.

These trends are driven by a combination of factors, said NIWA’s lead scientist for remote sensing, Dr. Matt Pinkerton.

“We suspect that changes in phytoplankton across the New Zealand shelf due to climate variability and change, the effects of coastal waves and storms on coastal erosion and resuspension of seafloor sediments, and changes in land use are all influencing these large-scale trends. On a smaller scale, what happens in the catchments Water and in rivers affects the clarity of water downstream in estuaries and on the coast,” said Dr. Pinkerton.

“Because of the damage that dissolved solids in high concentrations can cause, there is concern about the ecological and ecological impacts they have on our coastal marine area. This is particularly relevant because of the harsh winter weather we have just experienced – constant rainfall does not necessarily affect the concentration of TDS,” Dr. Pinkerton said. Sediments are in our oceans, but massive storms like the one the South Island saw in August could have a huge impact.”

The team used NASA’s Aqua MODIS satellite, which images the entire surface of Earth every one to two days. The data is free to use and has been used to study a wide range of topics, including glacier surface height and even the size of the Iberian wolf pack. In Aotearoa New Zealand, it has been used to monitor changes in ocean primary productivity for environmental reporting.

The NIWA report details 15 recommendations for improving the value of satellite remote sensing over the next five years. This includes the continuous use of satellite data along with in-situ sampling and modeling to develop the best ideas and manage future suspended coastal sediments.

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