by simon
Why are the oceans important? The importance of wildlife.

The importance of the oceans, their wildlife and ecosystems

The land and oceans are part of one system: Earth. So when we ask, why are the oceans important? We’re asking about our own future. Life began in the ocean billions of years before the first plants or animals colonised land. Oceans regulate the state of our atmosphere because they are 99 per cent of the volume of living space for animals and wildlife is the mechanism that drives stability.

Climate change has always been the symptom of biodiversity loss … that’s to say, the breakdown of the complex connectivity between lifeforms that allows Earth to flex in response to changing conditions. Ocean wildlife has, for the large part, acted as a buffer against the most catastrophic effects and since about fifty million years ago, has kept our climate quite stable.

Industrial fishing only happened recently in our planet’s history and this reduction in the abundance of wildlife represents our greatest challenge for survival.

Below you will find a range of articles designed to inspire an understanding of the magnitude of animal impact on our oceans.

What’s more important, the ocean or the land?

The importance we bestow on the land is anthropocentric because we live there. It’s naturally important to us that we protect it. Nonetheless, if life in the ocean dies, we suffer irreversible changes to land-based ecosystems and climate.

In this article, we take a look at many of the ways that land and oceans are linked together.

The answer to the question, ‘why are the oceans important’, is that we live on the land but the oceans regulate Earth’s temperature. The oceans are equally vital to the land we live on.

Latest posts about why the oceans are important

La Nina, drawing Simon Mustoe

There have been a few reports this year of Black Noddies washing up dead along Australia’s coastline. While we can’t rule out climate change effects, widespread seabird deaths during La Niña are not uncommon. There is a practical explanation. Nonetheless, whenever there is substantial mortality of adult seabirds, it may also be cause for concern.

In this post, I’ll explain a little bit about seabird population ecology and how it connects to ocean productivity and climate cycles.

La Niña and ocean productivity

During cooler La Niña conditions in the Pacific there is more surface productivity than during La Niño. You would think this means more food but as usual, ecosystems work differently to how we might imagine. Warm water floats and this usually forms a blanket over the sea, which stops many creatures from reaching the rich food beneath. You see, at the surface, sunlight, photosynthesis and food chains tend to use up all the nutrients quite quickly. When you see ‘blue water’ in the ocean, it’s a sign that the surface conditions are pretty bleak.

Widespread seabird deaths during La Niña could be cause for concern.
A Black Noddy feeds its chick on Heron Island. Photo, Simon Mustoe.

During La Niña years, the surface is cooler and this layer is spread thin. This means there is mixing of deeper layers and this promotes more nutrients reaching the surface and the water turns a bit green. There is a surplus of algae and zooplankton. For microscopic animals that live inside this layer, it’s rich pickings. They can have a bumper year. But for marine predators that feed on them, all the way up to sharks and seabirds, the situation is reversed.

Marine vertebrates need the strongest energy gradients

If you’re a predator searching for food, you need access to patches that are rich in prey such as flying fish and other filter-feeders. The problem is, when there is zooplankton everywhere, your prey is thinly spread out across large areas of ocean. You have to travel much further to find food and there comes a point when it’s no longer viable. La Niña years are not the greatest for breeding seabirds in particular. Black Noddies at Heron Island for example, have to return daily to their nests to incubate eggs and raise chicks.

El Nino, drawing Simon Mustoe
Warmer surface water pushes the nutrient-filled mixed layer deeper, meaning sharks and their prey, swim closer to the coast, where upwellings physically push the nutrients to the surface. Predators do well and prey are concentrated in hotspots.
La Nina, drawing Simon Mustoe
Cooler surface water means the nutrient-filled mixed layer is shallow. With a lot of food about, animals spread out across the ocean but it means density of prey is lower, which means a bumper time for prey but harder for predators to make a living.

The best breeding years are during El Niño, when the ocean is more barren. This forces fish to congregate in far higher densities around islands and upwelling zones. This is when the birds can reliably forage nearby and find ample food for their chicks. Also, the activity of the birds transferring nutrient to and from land, amplifies nutrient concentrations, effectively prolonging the season. The whole food chain flourishes during these conditions.

Living on the edge

One thing we always have to remember, is that wildlife lives on the very edge of survival. Seabirds congregate and feed in some of the lowest nutrient areas of the planet. Ironically, the ocean has some of the highest biomass. Not really ironic though, when you realise that is how and why it functions … it’s the absorption of energy into biological food chains that keeps ecosystems intact. That’s what animals do. But it also means that the more extreme changes in climatic conditions are going to cause significant mortality.

Boom bust cycles

Ecosystems need time to breathe. The boom bust cycles between La Niña and El Niño years give populations chance to recover. Fish disperse out into the ocean and mature, before congregating closer inshore to breed, then relaxing their distribution again. If climate change is having an effect, it’s in the duration and intensity of the peaks and troughs between these events. If they become too frequent, or not frequent enough, that is when it could start to impact whole populations of marine animals like seabirds.

Adult seabird deaths

Adult seabird mortality is a cause for concern because these are the birds that are most mature and connected to existing ecosystem processes. Seabird populations are split between adult breeders and adult non-breeders. Normally, there is a slow turnover of breeding adults as some die of natural causes and new adults are recruited to fill in the gaps. This provides a level of natural resilience against periodic environmental changes. What can also happen is that if too many adults die, the overall fitness of new recruits can drop below a viable level. When that occurs, it can lead to sudden population collapse – but due to the elasticity of seabird populations, these symptoms can take many years to reveal themselves.

This year there is a La Niña alert so what we’re seeing could be a sign of those conditions taking hold. At the same time, the amount of adult mortality is something to keep an eye on.

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