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
Lecturer in 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.
Are sandy beaches important ecosystems?
Sandy beaches support a range of unique species, some of which play particularly important ecological roles.
Sand eels, for example, are valuable as food for large fish, seabirds and marine mammals.
What’s more, sandy beaches act as important habitats for the younger stages of many commercially important fishes: beaches are critical in supporting populations of these species.
For example, two-thirds of UK flatfish landings are from species that rely exclusively on shallow (< 5m) sandy areas during juvenile stages.
Finally, sandy beaches are popular places to swim and some of the residents can be a hazard to bathers. Weever fish are a small, inconspicuous species that lies in the sand and delivers a meaty sting to beachgoers who step on them.
Weever fish
- Weever fish are small (up to approximately 15cm), mainly brown in colour, and have venomous spines on their first dorsal fin and gill cover.
- Weevers bury themselves in sand, just showing their eyes, and snatch prey as it comes past, which consists of small crustaceans and fish.
- Like some other species living in fast water flows, weevers do not have swim bladders and sink as soon as they stop actively swimming: this helps them remain on the bottom as the waves wash over them.
At first glance, the small, beige-coloured creatures are unremarkable, spending much of their time buried in sand. But when stepped on or handled, the spines on the dorsal fin and head can release powerful venom.
Are weever fish dangerous to humans?
Weever fish stings in themselves are not usually dangerous, but they can be very painful and can create difficulties when combined with other hazards – for example, currents or deep water.
Weever fish are surprisingly widespread and can be found in the surf zone of most beaches throughout the UK.
It is a good idea to wear hard-soled footwear such as water shoes or old trainers to avoid getting stung.
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If you do get stung, ask the lifeguard unit or someone with first aid training for assistance.
- If these options are not available you can treat yourself by submerging the affected area in warm water, as hot as you can stand, for at least 30 minutes: this tends to denature the venom.
What are the threats to sandy beach ecosystems?
Sandy beaches lie in coastal areas which are close to human pollution, construction and disturbance.
They are also subject to changes in the climate and storms which can completely reconfigure the physical environment.
We know very little about how these sandy beach ecosystems, and their important functions as habitats for juvenile fish, are changing.
What work is being done to better understand life on sandy beaches?
Our research at the University of Plymouth is investigating the role of sandy beaches as habitats for fishes – what makes beaches particularly good nurseries for juvenile flatfish and
where and when the risks from weever stings are highest.
We have constructed a long-term data set to resolve the natural dynamics in fish populations and to understand what impact humans are having.
We undertake sampling each summer, using a small hand-pulled trawl which we drag around in the surf zone – the fieldwork images featured on this page are from sampling on beaches in north Cornwall.
If you have visited beaches in Devon and Cornwall, you might have seen us. We count and measure what we catch and take some samples to understand what the fish are eating and how fast they are growing.
We also collect detailed information about aspects of the physical environment, including wave conditions, sediment characteristics, temperature, prey resources: this is allowing us to identify causes of variation in fish abundance, diet and growth.
Working closely with fisheries and conservation bodies, we provide scientific knowledge to support policy and management measures such as reference size limits and essential fish habitat.
Our work on sandy beaches is just one example of the extensive research on a wide range of fish habitats, undertaken at the University of Plymouth.
How can you get involved?
FinVision aims to develop and apply a novel camera system and citizen science framework to advance monitoring capabilities and collect data on habitat requirements of early juvenile fishes, including European sea bass and grey mullet, in inshore areas.
A smart underwater camera system is being deployed in the Plymouth Sound Marine National Park and surrounding areas using state-of-the-art scientific diving facilities at the University of Plymouth.
Visit the
FinVision interactive web portal
to see some of the footage being collected and help us to spot the fish.
Image credit: Ben Ciotti
Marine biology
Plymouth has an unrivalled location and reputation as a centre for marine biology.
A diverse range of rich coastal habitats – estuaries, sandy beaches, and rocky shores – are readily accessible for field trips and your own projects.
Marine Biology and Ecology Research Centre (MBERC)
Research in MBERC has contributed substantially to the understanding of how marine biodiversity is responding to environmental change and has informed management decisions at regional, national and international levels.
Members of the MBERC address a broad range of research questions, from the effects of environmental stress on microbes and developing embryos to the management of large scale impacts, such as global climate change.
