Some of you will have seen the images of thousands of stranded starfish on Southsea beach after Storm Angus earlier this week. The starfish were thrown onto the beach, some even reaching the promenade after the violent weather. The animals were then left stranded as the waves retreated and tide went out.
As Hannah Butt from Blue Reef Aquarium pointed out:
“Starfish feed on mussels and other molluscs and tend to live in relatively shallow water. Huge numbers of them can congregate on a single bed of mussels and – if conditions are right – will be dislodged by rough seas.”
Starfish more susceptible
As starfish feed in the shallows they are more at risk from the strong currents and wave action that can dislodge them and wash them ashore.
Starfish are one of many fascinating plant and animal species that live in the Solent and seas around the Isle of Wight. Other animals including jellyfish were also washed onto the beaches.
It is great that so many people took an interest in our marine life and tried to help although many animals were already dead having been exposed outside of the water for too long.
Whilst the sight of the stranded animals may have been harrowing, it is not all doom and gloom.
Stranding of marine creatures is a natural event that may happen after storms. It is related to a branch of science known as Disturbance Ecology. In this case the disturbance (Storm Angus) caused a change in environmental conditions that resulted in a change to the marine ecosystem. These disturbances often occur quickly and can have immediate effects on ecosystems and alter the natural community. Accordingly, disturbance events ultimately affect biodiversity. Biodiversity is the variety of organisms present in an ecosystem and events such as storms may actually have a role in maintaining biodiversity in the long term.
When certain species populations get disturbed it allows other species populations to increase e.g. removal of some starfish may provide some relief from predation for its prey. Standings like this also provide opportunistic foraging for other species and are part of typically dynamic coastal ecosystems.
A terrestrial example which is easy to visualise is that of a tree being blown over in a forest. If you imagine a large tree being blown over, the space it occupied then becomes available for other plants to colonise and the nutrients contained within the dead tree are recycled as it is eaten or decomposed.
The great concern for the marine environment is whether there are too many pressures on the marine world for Disturbance Ecology to have the associated positive impacts. The marine environment is heavily impacted by disturbances caused by people in addition to natural disturbances.
In the case of the Solent, the waters are next to areas with very high human population density. The local seas are a busy shipping route, used for extraction of aggregates, home to invasive species, important for fishing and popular for recreational pursuits such a boating. Multiple disturbances may lead to irreversible damage and even extinctions. Therefore, the effects of human caused disturbance need to be monitored to ensure they are not detrimental to marine life and it is vital to encourage the most sustainable practices when using these waters.
There are a few methods to reduce the pressures on the marine environment including reducing the amount of plastic we use and ensuring it is correctly disposed of so that it doesn’t enter the sea, picking sustainable options when selecting seafood, protecting vital habits such as seagrass beds and making sure that we do not disturb coastal wildlife such as nesting or feeding birds.