Ecology

What are seagrasses?

Seagrasses are a group of underwater plant species that resemble their terrestrial counterparts. Seagrasses can be found all over the world, but are generally limited to coastal waters since they are restricted by depth due to an important need for sunlight. Despite this, seagrasses are unrivaled in terms of productivity, creating some of the most unique and important ecosystems around the world.

Why are seagrasses important?

Seagrasses are known as “ecosystem engineers” due to their impact on shaping and modifying their local environments. One major service that seagrasses provide to their environment is blue carbon sequestration. Much in the same way trees remove carbon dioxide from the atmosphere, the blue carbon sequestration performed by seagrasses removes carbon dioxide from the ocean, mitigating ocean acidification. Dissolved carbon dioxide causes increased ocean acidity, which harms aquatic life. The blue carbon sequestered from coastal and marine ecosystems into seagrasses effectively converts harmful dissolved carbon dioxide into useful vegetative biomass.

Seagrass species distribution across the world, as reported by the Journal of Experimental Marine Biology and Ecology

Seagrasses play a critical role in maintaining the health of local marine ecosystems. Due to carbon sequestration, seagrass is a nutritious food source for animals such as sea turtles, manatees, dugongs, and migratory birds, thus influencing larger marine ecosystems around the world. Moreover, seagrass meadows serve as shelter for smaller marine animals such as shrimp, crabs, and fish larvae. Countless species rely on seagrasses, and many would find their survival in jeopardy if seagrasses were removed.

What threatens seagrass health?

Seagrasses are vulnerable to mass destruction and eradication. Human activity contributes to climate change, coastal development, and decreasing water quality, which threaten both seagrass populations and the species that rely on these marine ecosystems. Eutrophication is one of the most critical threats to seagrass. Eutrophication is the excessive growth of algae in bodies of water due to an influx of nutrients. Algal growth deoxygenates the local environment (effectively suffocating the local wildlife) and blocks sunlight to photosynthetic plants. The loss of this keystone species will damage all tiers of the ecosystem and also impact the organisms that rely on its services. Additionally, the elimination of seagrasses would have a significant economic impact, valued at a loss of US $19,002 per hectare per year.¹

Various threats to seagrass ecosystems and the resulting consequences of habitat destruction, sourced from ScienceMag

What are kelp forests?

Kelp are giant brown algae that live in shallow waters close to the shoreline and thrive in cold, nutrient-rich, clear waters that tend not to overlap with other marine vegetation systems. While they perform photosynthesis, kelp are not plants, as they lack roots, stems, and leaves, they are instead part of the algae family.

Why are kelp forests important?

Kelp forests provide homes for fish, invertebrates, and marine mammals in the same way forests do for terrestrial species. Because kelp has such a rapid growth rate (up to 18 inches per day), they create dense canopies that enable some marine species to use kelp forests to spawn offspring as a juvenile nursery habitat.

A significant benefit of kelp is greenhouse gas regulation. Kelp forests sequester carbon dioxide and release oxygen, mitigating ocean acidification. In addition to environmental benefits, kelp are also used in many beauty products and supplements due to both its rich nutritional value and its anti-inflammatory and antioxidant properties.

What threatens kelp forests?

Kelp are severely threatened by climate change. Longer, hotter summers and shorter winters mean fewer available nutrients for kelp. Various human activities such as coastal development, sedimentation, overfishing, commercial harvesting, and pollution also contribute to loss of kelp populations. The degradation of water quality from sewage, industrial disposal, and coastal runoff further threaten kelp forests as this reduces growth rates and reproductive success.

Click here to listen to Max Calloway, from the Washington Department of Natural Resources, express significant human impacts on kelp forest habitats.

Other climate change-driven phenomena also threaten kelp, such as high energy storms that can uproot plants and destroy entire habitats. El Niño Southern Oscillation events are examples of this kind of storm, which contribute to high ocean temperatures and strong wave energy, damaging many kelp forests in California.

Due to kelp’s critical role in their respective ecosystems, it is imperative to protect the forests of our oceans. The numerous benefits that they provide to ecosystems are crucial to the survival of marine organisms. Kelp restoration is long-underway and existing forests are being closely monitored by some of the nation’s elite oceanic research institutes.