The Roles of Aquatic Predators

Image Credit: Neil Hammerschlag, Image Cropped, CC BY-SA 2.0

Ecosystem Function and Services of Aquatic Predators in the Anthropocene (2019) Hammerschalg et al., Trends in Ecology and Evolution, https://doi.org/10.106/j.tree.2019.01.005

The Crux

Aquatic predators play an important role in many ecosystems, and are often among the more charismatic species in the ecosystem. Because of this, they are often the target of conservation for ocean management bodies worldwide. This paper aims to provide a synthesis of the ecosystem services that aquatic predators provide in marine and freshwater ecosystems worldwide, both for that ecosystem and for the humans that use it. Below, we’ve chosen four of the more interesting and important roles to go into.

The Findings

Mediating Climate Change

Aquatic plant life holds large amounts of carbon, and higher levels of plant consumption lead to more of this carbon getting into the atmosphere. Aquatic predators can keep herbivore populations at reasonable levels, ensuring the “sequestering” of large amounts of carbon. A great example is the recovery of sea otters in the pacific Northwest. The rebounding otter population lowered the numbers of sea urchins, which in turn led to an increase in kelp, which has increased the amount of sequestered carbon in the area by between 4 and 9 megatons.

Did You Know: Review Papers

Clearly this Paper of the Week is slightly differently formatted. Whilst we usually look at original experiments here on Ecology for the Masses, we’ve chosen to summarise a review paper this week. Review papers are the result of an exhaustive synthesis by researchers who want to summarise the state of research in a specific field. They’re essentially a goldmine for anyone looking to get up to speed on a topic. As a result of their nature as summaries, they’re generally quite accessible to non-scientists as well, so we highly recommend checking out the original paper here.

Ecosystem Engineers

Ecosystem engineers are species capable of creating or modifying entire habitats through their actions (humans and elephants are great examples). The activities of species which burrow or dig out benthic areas modify seafloor or lakebed habitats considerably. Carcasses that aquatic predators leave behind create habitats by themselves, with whale carcasses especially creating microhabitats that sustain many species. The rise of the whaling industry saw a reduction in these habitats, and many species have been theorised to have gone extinct as a result of the lack of whale carcasses.

Mediating Species Invasions

Often, aquatic predators are the invasive species that native ecosystems have to worry about. However there is some evidence to suggest that local aquatic predators can suppress alien species populations. Whilst some alien species may outcompete other species, if there is a predator to which that alien species has not evolved defenses, the alien’s negative effects on competitors might not be as severe.

Bioinspiration

This is one that I hadn’t heard much about prior to this paper. Aquatic predators adaptations and traits often serve as inspiration for technological innovation. Examples include shark skin, which can improve hydrodynamic performance, and the skin of marine mammals, which inhibits ‘fouling’ matter. When applied to marine technology this could significantly reduce both transportation and cleaning costs.

What’s Left?

There are significant gaps in our knowledge regarding aquatic predators. Many whales and shark species in particular are under-researched. The role of sharks as exerters of trophic pressure is not fully understood, and there is substantial room for expansion of work on the suppression of invasive species. We’ve only just scratched the surface of using these taxa for bioinspiration, and forthcoming advances in technology will hopefully lead to exponential growth in knowledge here.

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