Slight modifications to sea defences – at little or no extra cost – can boost the level of biodiversity found in intertidal zones, a study has shown.
Researchers found that attaching artificial rock pools to the structures created habitats suitable for mobile creatures, such as starfish or crabs.
They added that they hoped the results would encourage future designs to incorporate “ecological engineering”.
The findings have been published in the Marine Ecology Progress Series journal.
“When we looked into the economics, more than 80% of money that is spent to protect coastlines from climatic changes is spent building new sea walls, increasing the height, stability and length of existing ones,” explained co-author Mark Browne, an ecologist based at the US-based National Center for Ecological Analysis and Synthesis.
“This is because we want to protect human lives and we also want to protect the important infrastructure.”
“But when we looked at how those seawalls were being built, they were being built according to engineering and financial criteria, not really on their capacity to support marine life.”
Dr Browne, who was based at the University of Sydney for the research, said colleague and co-author Prof Gee Chapman had spent many years examining how plants and animals found in the intertidal area of shorelines were affected by engineering.
“The overwhelming evidence she had was that there were major differences between the types of organisms that you find on seawalls compared with those on natural shorelines,” he said.
“One of the major differences was the absence of mobile organisms – such as limpets, starfish and crabs.”
So the researchers set up an experiment to find out why this was the case and what could be done to mitigate the impact of the structures.
Previous studies had shown that when artificial shorelines replaced the natural ones, there was usually a change of species locally as sedimentary habitat was replaced with hard materials.
“Although many native species live on the hard substratum, they are not usually the same species that live in or on soft substratum,” they wrote.
They suggested that the changes to the composition of organisms living on or near the structure may be the result of the steep sides of the sea defences, limiting the intertidal area available to species.
“Alternatively, the walls may lack important intertidal habitats microhabitats,” they added. “The most obvious are rock pools.”
In order to test the idea whether simple additions to otherwise featureless sea walls in Sydney Harbour would make the structures more biodiversity friendly, the researchers installed a number of large, concrete flowerpots to create artificial rock pools.
They observed: “The size of the pot, its height on the wall and its location affected the assemblages that developed, with greater abundances and diversity of organisms in shallower pots and those at mid-shore levels.”
Dr Browne explained: “We have shown quite clearly that you are able to improve levels of biodiversity by more than 110% and the size of the pot and the location it is situated matters.
“If we are going to be spending more than US $144bn each year to build new [flood defences] or increase the height or stability of existing ones and 80% of those funds on coastal defences, we really need to be starting to think about how we can put these types of ecological engineering approaches into practice.
“The measures can be added to the work with little or no additional cost without diminishing the integrity of the structure.”
The life of a Great White Shark
The great white shark, known scientifically as Carcharodon carcharias, embodies the apex predator of the ocean. This majestic creature’s life is a testament to survival, adaptability, and the intricate balance of the marine ecosystem.
Born in the waters off coastal regions, a great white shark begins its life as a pup within the safety of nurseries, typically found in warm, shallow waters. The pups, measuring around 5 feet in length at birth, are immediately equipped with an innate instinct for survival.
As they grow, great whites embark on a journey, venturing into deeper and cooler waters, often covering vast distances across the ocean. These apex predators are perfectly adapted hunters, relying on their impressive senses to detect prey. Their acute sense of smell, aided by specialized sensory organs known as ampullae of Lorenzini, helps detect the faintest traces of blood in the water from several miles away.
Feeding primarily on seals, sea lions, and other marine mammals, great whites are known for their powerful jaws lined with rows of razor-sharp teeth. Their hunting techniques often involve stealth, utilizing their streamlined bodies to approach prey from below and striking with incredible speed and force.
Despite their fearsome reputation, great whites play a crucial role in maintaining the health of marine ecosystems. As top predators, they help regulate the population of prey species, preventing overpopulation that could disrupt the balance of the food chain.
Reproduction among great white sharks is a slow and careful process. Females reach sexual maturity between 12 and 18 years of age, while males mature earlier, around 9 to 10 years old. Mating occurs through complex courtship rituals, with females giving birth to a small number of live pups after a gestation period of about 12 to 18 months.
However, the life of a great white shark is not without challenges. Human activities, including overfishing, pollution, and habitat destruction, pose significant threats to their population. Additionally, despite their formidable presence, great whites are vulnerable and face dangers from entanglement in fishing gear and accidental bycatch.
Despite these challenges, great white sharks continue to inspire awe and fascination among scientists and nature enthusiasts. Their presence in the ocean serves as a reminder of the delicate balance and interconnectedness of marine life, emphasizing the need for conservation efforts to protect these magnificent creatures for future generations to admire and study.
Want to learn more about sharks? Visit The Shark Trust website: www.sharktrust.org
Book Review: Sea Mammals
This is a book packed with information about some of the most iconic and charismatic marine species. I have a particular soft spot for the pinnipeds, seals and sea lions, due to some incredible diving encounters over the years. So these were the pages I first turned to.
Once picked up this book is hard to put down. Polar Bears, Narwhal, Sea Otters, manatees, whales and dolphins adorn the pages with beautiful photographs and illustrations. Each turn of the page lures you in to discover more about a species you love, one you want to learn more about, some you have never heard of and even includes the details of fascinating animals that are sadly now extinct.
I think what I love most about this book is how it is organised. Rather than simply lump the animals into taxonomic groupings, they are put into chapters that tell you a story about them. Whether it is the story of their evolution, how they were discovered, their biology, behaviour or need for conservation. Once you have decided on an animal to delve deeper into, each species has its own story, as well as key information about size, diet, distribution, habitat and conservation status.
There is plenty to enjoy in this delightful book. Plenty to learn too. As the cold dark nights draw in, I can see myself delving into this book time and time again. This is a perfect gift for anyone that loves the ocean and its inhabitants. Or just treat yourself.
What the publisher says:
From the gregarious sea otter and playful dolphins to the sociable narwhal and iconic polar bear, sea mammals are a large, diverse, and increasingly precious group. In this book, Annalisa Berta, a leading expert on sea mammals and their evolution, presents an engaging and richly illustrated introduction to past and present species of these remarkable creatures, from the blue whale and the northern fur seal to the extinct giant sperm whale, aquatic sloth, and walking sea cow.
The book features more than 50 individual species profiles, themed chapters, stunning photographs, and specially commissioned paleo-illustrations of extinct species. It presents detailed accounts of these mammals’ evolutionary path, anatomy, behavior, habitats, and conservation. And because these are key species that complete many food chains and have the widest influence of all sea life, the book also offers insights into a broad variety of marine worlds today and in the future.
About the Author:
Annalisa Berta is professor emerita of biology at San Diego State University. A specialist in the anatomy and evolutionary biology of marine mammals, especially baleen whales, she formally described a skeleton of the early pinniped Enaliarctos. She is the author of Return to the Sea: The Life and Evolutionary Times of Marine Mammals and the editor of the award-winning Whales, Dolphins, and Porpoises: A Natural History and Species Guide.
Publisher: Princeton University Press
Published: 26th September, 2023
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