Want to keep learning?

This content is taken from the University of Southampton's online course, Beneath the Blue: The Importance of Marine Sediments. Join the course to learn more.

Skip to 0 minutes and 4 secondsMARTIN SOLAN: The organisms that inhabit our coasts and our shelf seas are integral to many of the things we, as humans, ultimately rely upon. So it's important for us, as marine ecologists, to understand their interactions, where they live, and how things might change in the future as our climate is changing. As we will learn, biodiversity is the variety of life within a location and between locations. It comprises of genetic diversity, of ecosystem diversity, and species diversity. In a dynamic environment like the one I'm sitting in today, it's quite easy to connect species to particular locations, to particular processes. But we can see all of those species' interactions.

Skip to 0 minutes and 46 secondsWe can see the same processes and the same [INAUDIBLE] within marine sediments and study those in situ, just like we can here. One of the advantages of being down on a rocky shore is the diversity of organisms that are here, both in terms of algae and in terms of different invertebrates. And if you look around in the pools, we can study a variety of green algae, of red algae, calcareous algae, and various invertebrate groups that live kind of in and amongst all the different rocks. And we can study that diversity as it changes across the gradient, from the high shore to the low shore.

Skip to 1 minute and 22 secondsAnd we can also use those animals and algae to explore their adaptations to what is, for them, quite an extreme environment.

What is biodiversity and why is it important?

Biodiversity (short for biological diversity) is the variety and variability of biological life across the world. It refers to the number and abundance of species present within a given habitat or ecosystem and is made up of 3 interwoven factors: Ecosystem diversity, species diversity and genetic diversity.

Biodiversity is not constant across the world. The distribution and abundance of species varies globally and within regions. Broadly speaking biodiversity is highest in the tropics and declines as we move towards the poles. There are various factors that influence the distribution of biodiversity. These include environmental factors such as temperature, depth, freshwater input, organic input and sediment type, as well as biological factors such as how species interact with each other (e.g. predation). The 2010 Census of Marine Life project catalogued and mapped biodiversity across the world’s oceans. You can see a depiction of this in the image below. The colour scale shows increasing marine biodiversity from blue (low biodiversity) to red (high biodiversity).

A global map with a grid overlay. Grid boxes are colour-coded according to level of diversity, with blue (lowest diversity) zones in the polar regions and red (highest diversity) zones located in the western Indian and eastern pacific oceans, and around the coasts of India and South Africa.Map of marine biodiversity. © Tittensor et al., Nature (2010).

High species diversity is important for the processes and functions of all ecosystems, whether terrestrial or marine, mountain top or deep sea trench. This is because biodiversity is good at packaging nutrients, energy, matter and information, and transferring it between compartments. An example of this can be seen in the carbon cycle.

All species, whether plants, animals, or microscopic organisms, are integral to regulating a variety of ecosystem processes and functions, which in turn sustain goods and services that humans rely on. These include providing clean air, food, pollination of crops and the regulation of pathogens, all of which are imperative for human standards of living and well-being.

However, the provisioning of these goods and services is threatened by the current rates of species loss, sometimes also referred to as the crisis on biodiversity or the sixth mass extinction (in Earth’s history). Given the role that species play, a decline in diversity may have serious consequences for many of the major processes that our ecosystems rely on.

The reason species may go extinct are varied and complex. Species differ in sensitivity and therefore have different tolerances to environmental stressors depending on the type (e.g. trawling, plastic, heavy metal pollution, ocean warming and acidification), duration (press, pulse) intensity of stress (high, low) they experience.

The worst case scenario would be random extinction events, where any species can go extinct at any time. However the reason species tend to go extinct is due to specific circumstances, such as physical disturbance, changes in environmental conditions, introduction of competing species or habitat loss. However it’s not all doom and gloom as some species do respond to change in positive ways.


Examine the world map of marine biodiversity near the top of this step. Is it what you expected to see? Is there anything about the distribution of biodiversity that surprised you?

Share this video:

This video is from the free online course:

Beneath the Blue: The Importance of Marine Sediments

University of Southampton