Life beneath the paddleboard: the hidden ecology of our beach destinations
From surf-riding clams to weever fish – Dr Benjamin Ciotti explores the dynamic environment of surf zone ecosystems
Dr Benjamin Ciotti
Associate Professor of Marine Biology
School of Biological and Marine Sciences (Faculty of Science and Engineering)
A surprising amount. Beaches look a bit like empty deserts, but a wide range of species make their living here.
Invertebrates like crustaceans, worms and molluscs can be found buried in the sand. Those such as beach fleas, shrimps and crabs move about on the surface at low tide.
Below the water, the surf zone supports a number of fishes, crabs, shrimps and cephalopods.
Plants and algae are less visible than on some other coastal habitats such as seagrass beds, saltmarshes or kelp forests, but there can be substantial algal communities living on or among sand grains or floating in the water: these support substantial food webs in some cases.
What is the environment like for organisms living in the surf zone?
It’s a very dynamic and, in some respects, harsh environment.
Imagine yourself the size of a small fish or crab: you would experience huge breaking waves many times your own body height, strong currents and harsh, abrasive storms of wave- or wind-blown sand.
The tide would rush in and out exposing you to extremes of temperature, and the sand would constantly be mixed and moved.
There wouldn’t be all that many places to hide from predators either, unless, of course, you are a burrower.
How do organisms cope with these dynamic conditions?
Most species on sandy beaches are specially adapted for life in this environment. They have innovative ways to control their position despite the strong water flows and tides. They also have ways to avoid being seen and find food sources that might be scarce or dispersed.
Flatfishes have a flattened shape that allows them to hug the bottom. They can also bury rapidly, like many resident crabs, shrimp and other fish such sand eels and weever fish. These adaptations help sandy shore organisms escape hydrodynamic forces and keep out of sight of predators.
Sandy shore species are often well camouflaged and may undertake extensive migrations up shore when the tide comes in to escape predators or access food resources. In young flatfish, this can involve moments of several kilometres over the course of just a few hours.
There are even ‘surf-riding’ clams and crabs that use waves to wash them up and down the beach and can bury rapidly between waves to stay in position.
