Seabed monitoring for biodiversity management

Global marine biodiversity is continually threatened by oceanographic changes linked to both global warming and anthropogenic activities that degrade the ambient environment of marine organisms. Australia’s ocean biodiversity is admired around the world, and new initiatives are being undertaken to help conserve marine ecosystems for decades to come, both locally and globally.

This fuels a global initiative, the Ocean Decade, which aims to transform our planet’s seascape for the better by 2030, including eliminating ocean pollution, mapping ecosystems, targeting marine hypoxia (oxygen-depleted concentrations), sustainably harvesting food to support society and protecting. communities from ocean hazards (such as tsunamis).

Extending up to 200 nautical miles (~370 km) from Australia’s entire coastline, the exclusive economic zone encircles the continent, almost half of which contains protected areas known as Australian Marine Parks. These parks have recently become the focus of increased monitoring to identify key pressures facing the organisms that inhabit them, thereby encouraging the implementation of new stewardship strategies.

New research published in Frontiers of Marine Science has turned to seafloor mapping to generate habitat maps that can be monitored for decades to identify significant changes that could pose dangers to local wildlife.

The AusSeabed program is a national initiative launched in 2018 that compiles bathymetric data (the underwater equivalent of topography, studying the depths of the ocean floor) to produce geomorphometric maps that can be used to predict scale and location of particular biological assemblages, as well as their differences over time.

With previous research suggesting that topographic features of the ocean can impact the thermal and nutrient mixing of the ocean up to 1 km away, this is particularly useful in the case of deep-sea benthic communities that might otherwise be difficult to monitor in relatively inhospitable environments. .

Dr Vanessa Lucieer, associate professor at the University of Tasmania, and colleagues have produced geomorphometric maps for 37 of Australia’s 61 marine parks, a quantitative approach to assessing the landforms making up the seafloor. Bathymetric data covered approximately 58% of the area of ​​the marine parks, reaching up to approximately 86% on some of the continental slopes where a greater concentration of exploration had already taken place.

The geomorphometric characteristics of the maps were divided into 10 classes: summit, ridge (elongated highest point), trough (elongated, wide, flat-bottomed channel), plane (flat surface), hole, valley, slope, apron (a gentle slope at the base of a high climax), the escarpment (steep slope between shallow slopes), and the saddle (broad dip within a high climax).

In marine parks, plane was the most common bathymetric feature (~58%), followed by slope at ~18%, with apron, saddle and valley accounting for up to 8% of the mapped area. For the southwest and southeast marine parks, the flat seafloor was up to approximately 33% less prevalent compared to all other areas, instead experiencing an increase in ridges, troughs, and valleys.

Additionally, there was a pronounced difference in bathymetric characteristics by depth zone, with the research team selecting two key foci in the mesophotic zone (~30 m to 70 m) and the upper slope (200 m at 700 m). Only 24 of the 37 marine parks have bathymetric data in the mesophotic zone, of which 16 were predominantly planar with small sections of slope and apron, while the other eight had ups and downs with ridges, peaks, holes and valleys interspersed. Conversely, the deeper slope upper zone had a much more varied profile across all the different bathymetric features.

Understanding the different bathymetric profiles of the ocean allows targeted management strategies for each unique marine park, while identifying those with similar characteristics allows effective measures and resources to be shared between them.

The mesophotic zone, as well as the rariphotic zone (70 to 150 m deep), constitute key habitats for fish and are therefore subject to pressure from industrial fishing practices. Determining fish habitat preferences in these areas therefore means that policymakers can target conservation efforts in appropriate areas to protect both the natural world and sustainable food supplies.

Similarly, ridges are known to be points of great biodiversity, so identifying their location around Australia, which is already under threat from increased marine degradation, is a key factor in targeting habitat and organism conservation efforts who live there.

Although this research marks an important first step in the use of geomorphometry for ecosystem monitoring and management, it is inherently biased by the quality and coverage of available bathymetric data, which should be an additional focus for acquisition data in the future.

As efforts to conserve Earth’s marine world continue to grow, they are continually challenged by the rapid pace of ocean transformation, and scientists must continue this important work to seek the positive changes needed to ensure the prosperity of the world. our oceans for centuries. come.

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