A casual glance at the ocean and you may just see a mass of blue. But take a closer look. There are waves, different colours, and different levels of water clarity. If you could peel back the layer of water, you would see environments that are not entirely alien – like mountains, canyons, forests, grass meadows, sand, mud, and volcanoes.
The ocean is a mosaic of the most wondrous and splendid habitats, hosting a magnificent array of life. Whilst the terrain itself may remain fairly stable, the ocean itself moves. It’s not just the waves you can see breaking on the beach, nor the movement of the tides, or even those rip currents you really don’t want to find yourself stuck in. Beneath the surface you will also find movement – like currents flowing at different depths, upwellings that bring cold, nutrient rich waters to the surface, and internal waves as tall as 244 meters. Sometimes you get two water masses moving either towards or way from each other, creating oceanic fronts. Broadly speaking there are two types of oceanic fronts. Convergent fronts occur when the masses move towards each other. Here the water tends to be warmer than the surrounding area, and accumulate all sorts of marine critters, algae, and even litter. In divergent fronts, where the water masses are moving away from each other, upwellings are created bringing up nutrients from the deep. These nutrients support phytoplankton growth, which in turn supports zooplankton, which in turn supports other marine life – including species under threat such as the loggerhead sea turtle (Caretta caretta), and species we enjoy eating, like albacore tuna (Thunnus alalunga).
As with many oceanographic features fronts are not necessarily permanent features – they do not stay in exactly the same place, in perpetuity. The ocean is a highly dynamic environment and as a result, the conditions that define the habitats for many marine species – particularly pelagic species that live in the water column – are also constantly on the move…
The full article was published in – and can be read in – Biosphere Magazine.
Image: Loggerhead Turtle. Credit Debora Sujono/Flickr (CC BY-NC-ND 2.0)