#biostudent – BioQuakes

A new study has found that the presence of invasive rats on tropical islands is affecting the territorial behavior of fish on surrounding coral reefs. The rats, which arrived on the islands as stowaways on ships in the 1700s, change the behavior of jewel damselfish, a herbivorous species of tropical reef fish that “farm” algae in the branches of corals.

The study, which was led by scientists from Lancaster University in the UK and involving researchers from Lakehead University in Canada, was published in Nature Ecology and Evolution and compared five rat-infested and five rat-free islands in a remote archipelago in the Indian Ocean. The rats disrupt an important nutrient cycle by attacking and eating small resident seabirds and their eggs, leading to a drop-off of nutrients in the seas surrounding rat-infested islands. This results in a lower nutrient content of seaweed for herbivorous fish, such as the damselfish. The damselfish around rat-infested islands behave less aggressively and need to have larger territories due to the lower nutrient content of the algae.

Seabirds travel out into the open ocean to feed and return to nest on islands. The seabirds then deposit nutrients, through their droppings, onto the islands, and many of these nutrients are subsequently washed into the seas, fertilizing the surrounding coral reef ecosystems. On islands with invasive rats, the rodent populations decimate the seabirds, leading to seabird densities that are up to 720 times smaller on rat-infested islands. This results in much less nitrogen flowing onto the coral reefs around these islands.

Around islands with intact seabird populations, the farming damselfish aggressively defend their small patch, typically less than half a square meter, of the reef to protect their food source – turf algae. However, the scientists observed that farming damselfish on reefs adjacent to rat-infested islands were much more likely to have larger territories and were five times more likely to behave less aggressively than those who lived on reefs adjacent to islands without rats. The damselfish around rat-infested islands need to have larger territories because the algae around rat-infested islands is less nutrient-rich due to the missing seabird-derived nutrients.

This behavior change in the damselfish could potentially have wider implications for the spread of different species of coral, the distribution of other reef fish, and the resilience of damselfish over generations due to changes in hereditary traits. Changes in behavior are often the first response of animals to environmental change and can scale up to affect how and when species can live alongside one another. This study is the first to show that invasive rats can change the behavior of coral reef fish in this way and highlights the importance of understanding and managing the impacts of invasive species on ecosystems.

Students in our AP Biology class are likely to be familiar with these concepts of nutrient cycling and the importance of nutrients in supporting the growth and productivity of an ecosystem. The study highlights how the nutrient cycle on coral reefs is disrupted by the presence of invasive rats, leading to a drop-off in nutrients in the surrounding seas and a lower nutrient content of seaweed for herbivorous fish. This can have consequences for the growth and productivity of the coral reefs and the overall health of the ecosystem.

In the pandemic’s early days, countries reported their COVID-19 levels daily. However, that isn’t the case now. In 2022, countries most often report their COVID-19 infection and vaccination levels only five days a week. Despite this, there are still outbreaks of the virus. China, however, has a strict zero COVID-19 policy which results in lockdowns when too many cases are reported. This means that Chinese citizens often find daily life disrupted by the presence of COVID, an experience that we Americans have left more or less in the past.

This begs the question, which course of action should be adopted by countries worldwide? Of course, a middle ground would be ideal, however, that may be unrealistic as governments are trying to find a “new normal” (as the UK put it). Despite this hope to live with COVID, many people are outraged at what seems to be complacency coming from international governments, as citizens say that more needs to be done. What more is there to be done, though? Besides going back to the early ways of the pandemic, reporting cases and deaths daily, governments worldwide are doing everything possible to keep people informed on both COVID and its effects.

China’s lockdowns, while effective, are very extreme by international standards. There is a call from citizens in China asking for the COVID-19 protocols to be lessened, as the lockdowns are affecting people’s livelihoods. There are small wins, as the Chinese government has slightly repealed COVID-19 protocols, as citizens no longer need to show a negative covid test to use public transport. A study showed that when intrusive protocols are introduced, people overall show “non-compliance in applying health protocols” meaning that while China’s health practices may be effective for now, they may mean trouble in the long run as people stop following them. This supports the idea of a happy middle ground between the United States’ and China’s current protocols.

BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: #biostudent

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