Man-made underwater sounds may affect marine ecosystem

Underwater sounds linked to human activity could alter the behaviour of seabed creatures that play a vital role in marine ecosystems, a new study has found.
In the study, exposure to sounds that resemble shipping traffic and offshore construction activities resulted in behavioural responses in certain invertebrate species that live in the marine sediment.
These species make a crucial contribution to the seabed ecosystem as their burrowing and bioirrigation activities (how much the organism moves water in and out of the sediment by its actions) are crucial in nutrient recycling and carbon storage.
The study by University of Southampton in UK showed that some human-made sounds can cause certain species to reduce irrigation and sediment turnover.

Such reductions can lead to the formation of compacted sediments that suffer reduced oxygen, potentially becoming anoxic (depleted of dissolved oxygen), which may have an impact on seabed productivity, sediment biodiversity and also fisheries production.
"Coastal and shelf environments support high levels of biodiversity that are vital in mediating ecosystem processes, but they are also subject to noise associated with increasing levels of offshore human activity," said lead author Martin Solan, a professor in Marine Ecology.

The researchers studied three species - the langoustine (Nephrops norvegicus), a slim, orange-pink lobster which grows up to 25cm long, the Manila clam (Ruditapes philippinarum) and the brittlestar (Amphiura filfiformis).

They were exposed to two different types of underwater sound fields - continuous broadband noise (CBN) that mimics shipping traffic and intermittent broadband noise (IBN) reflecting marine construction activity.
The sounds were reproduced in controlled test tanks. For CBN, a recording of a ship made in the English Channel at a distance of around 100 metres was used.
For IBN, a recording of a wind farm in the North Sea at a distance of about 60 metres was used.
With the langoustine, which disturbs the sediment to create burrows in which it lives, the researchers saw a reduction in the depth of sediment redistribution (how much of the surface sediment was overturned into the deeper layers) with exposure to IBN or CBN.

The Manila clam, a commercial fishery species in Europe that lives in the sediment and connects to the overlying water through a retractable siphon, reduced its surface activity under CBN, which affected the surface roughness of the sediment.
Bioirrigation, which is strongly influenced by clam behaviour and the activity of the siphon, was markedly reduced by CBN and slightly reduced under IBN.
However, the sound fields had little impact on the brittlestar.
The study was published in the journal Scientific Reports.