Q&A: Toxic algae, warming waters imperil marine life on U.S. coasts

The Impact of Toxic Algae Blooms on Marine Ecosystems

The images are heart-rending: hundreds of dolphins and sea lions washing up along the shores of Southern California, sick and dying from toxic algae poisoning. Photographed earlier this summer, they are the latest reminders that the climate crisis is becoming impossible to ignore.

Toxic algae blooms, a recurring natural phenomenon, have long been observed in water off the coast of Southern California. But scientists are increasingly concerned over the frequency and severity of these deadly algal outbreaks. As climate change continues to warm ocean temperatures, these favorable conditions allow harmful algae to proliferate.

Experts’ Insights

USC News spoke with David Caron, an expert in biological oceanography who is closely examining the ecological crisis and its potential impact on local marine ecosystems, and Carly Kenkel, at the USC Dornsife College of Letters, Arts and Sciences, who focuses on coral reefs.

Domoic Acid and its Impact on Marine Species

Caron: Beyond marine mammals, sea birds that feed on small fish such as anchovies and sardines are at risk for significant intake of toxins if the planktivorous fish they prey on are consuming toxic algae. Most fish and shellfish appear to possess a reasonable tolerance for domoic acid (although some may be affected), but contaminated fish, particularly filter-feeding shellfish, pose a significant health risk to marine animals — and humans — that might consume them.

But not all algal blooms are harmful. Many are beneficial and support aquatic food webs. When those blooms are dominated by algal species that are noxious or toxic, however, they can result in very harmful effects on biota.

Changes in Toxic Algae Blooms due to Climate Change

Caron: There is growing evidence for shifts in the latitudinal distributions of toxic algae along the U.S. West Coast that appear to be driven by changes in temperature (i.e., a warming ocean). However, overall, temperature plays a secondary role to nutrients in explaining the occurrence of algal blooms in general and toxic blooms in particular. The availability of essential nutrients such as nitrogen, phosphorus and some trace nutrients such as iron is key to understanding the location, frequency and severity of coastal algal blooms, and that extends to toxic blooms in freshwater ecosystems as well.

Usually, when one talks about “bloom-forming nutrients,” the elements nitrogen and phosphorus are most discussed. Those two elements are needed in significant quantities for producing biomass, but generally, they are in the shortest supply for algae in many ecosystems. Thus, nitrogen and phosphorus tend to have a “controlling influence” on the magnitude of algal blooms.

There are natural sources of nutrients, generally arising from the decomposition of dead organic material, but also man-made sources. Sewage, agricultural and domestic animal facilities, and urban runoffs tend to have very high concentrations of these elements. In waters where man-made sources are significant relative to natural sources, they can lead to or augment algal blooms.

The Importance of Coral Reefs for Ecosystems

Kenkel: Corals are the foundation of tropical reef ecosystems. Reefs are incredibly biodiverse — like rainforests of the sea. They are home to 25% of all marine species. But they also play several other roles. They act as a natural breakwater and can prevent erosion and waves and are a major source of income from tourism and livelihoods around the world through subsistence fishing.

Current State of Coral Reefs

Kenkel: Right now, the Caribbean is experiencing an unprecedented heat wave. We’re seeing signs of major coral stress everywhere from Florida to Belize to the eastern tropical Pacific. The Florida Keys reef tract — the third largest barrier reef in the world — has not experienced temperatures this extreme in at least 40 years. The effects are particularly bad in the lower Florida Keys, where we do most of our research. Just this week, we had to mobilize to sample a long-term field transplant experiment early. The experiment was originally planned to run until next October, but the corals are unlikely to survive until then.

The Urgency of Climate Change and Coral Conservation

Kenkel: I think it’s really the reef ecosystems that inspire. While the coral itself is beautiful, my sense is that it’s the diverse array of fish and other animals that inhabit the reefs that truly bring the system to life. I think it’s all that diversity, together, that brings joy and inspires action.

Climate change is a global problem, and we’re seeing these extreme heat events because of how much carbon dioxide is currently in our atmosphere. Every bit helps — taking public transit, buying locally, turning up your air conditioning just a few degrees, and, for those who can afford it, opting for clean-air or all-electric vehicles and installing solar panels and battery storage systems that will reduce your carbon footprint.

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• Sustainability

SDGs, Targets, and Indicators

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The issues highlighted in the article are connected to SDG 14: Life Below Water, SDG 13: Climate Action, and SDG 15: Life on Land.

2. What specific targets under those SDGs can be identified based on the article’s content?

• Under SDG 14: Life Below Water, the specific target is Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities, including marine debris and nutrient pollution.
• Under SDG 13: Climate Action, the specific target is Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters in all countries.
• Under SDG 15: Life on Land, the specific target is Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• For Target 14.1 under SDG 14: Life Below Water, the article mentions the impact of toxic algae blooms on marine animals. The indicator that can be used to measure progress towards this target is Indicator 14.1.1: Index of coastal eutrophication and floating plastic debris density.
• For Target 13.1 under SDG 13: Climate Action, the article discusses the impact of climate change on ocean temperatures and the occurrence of algal blooms. The indicator that can be used to measure progress towards this target is Indicator 13.1.1: Number of deaths, missing persons, and directly affected persons attributed to disasters per 100,000 population.
• For Target 15.1 under SDG 15: Life on Land, the article highlights the importance of conserving and restoring terrestrial and freshwater ecosystems. The indicator that can be used to measure progress towards this target is Indicator 15.1.2: Proportion of important sites for terrestrial and freshwater biodiversity that are covered by protected areas, by ecosystem type.

4. SDGs, Targets, and Indicators

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Source: news.usc.edu

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