Kelp forest

Kelp forests are underwater areas with a high density of kelp, which covers about 25% of the world’s coastlines. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds.– Charles Darwin, 1 June 1834, Tierra del Fuego, Chile Kelp forests are underwater areas with a high density of kelp, which covers about 25% of the world’s coastlines. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds. Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were also discovered in tropical waters near Ecuador. Physically formed by brown macroalgae, kelp forests provide a unique, three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns and provide many ecosystem services. However, the influence of humans has often contributed to kelp forest degradation. Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae. This can rapidly result in transitions to barren landscapes where relatively few species persist. The implementation of marine protected areas is one management strategy useful for addressing such issues, since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors. The term kelp refers to marine algae belonging to the order Laminariales (phylum: Heterokontophyta). Though not considered a taxonomically diverse order, kelps are highly diverse structurally and functionally. The most widely recognized species are the giant kelps (Macrocystis spp.), although numerous other genera such as Laminaria, Ecklonia, Lessonia, Alaria, and Eisenia are described. A wide range of sea life uses kelp forests for protection or food, including fish. In the North Pacific kelp forests, particularly rockfish, and many invertebrates, such as amphipods, shrimp, marine snails, bristle worms, and brittle stars. Many marine mammals and birds are also found, including seals, sea lions, whales, sea otters, gulls, terns, snowy egrets, great blue herons, and cormorants, as well as some shore birds. Frequently considered an ecosystem engineer, kelp provides a physical substrate and habitat for kelp forest communities. In algae (kingdom Protista), the body of an individual organism is known as a thallus rather than as a plant (kingdom Plantae). The morphological structure of a kelp thallus is defined by three basic structural units: In addition, many kelp species have pneumatocysts, or gas-filled bladders, usually located at the base of fronds near the stipe. These structures provide the necessary buoyancy for kelp to maintain an upright position in the water column. The environmental factors necessary for kelp to survive include hard substrate (usually rock or sand), high nutrients (e.g., nitrogen, phosphorus), and light (minimum annual irradiance dose > 50 E m−2). Especially productive kelp forests tend to be associated with areas of significant oceanographic upwelling, a process that delivers cool, nutrient-rich water from depth to the ocean’s mixed surface layer. Water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout the water column. Water clarity affects the depth to which sufficient light can be transmitted. In ideal conditions, giant kelp (Macrocystis spp.) can grow as much as 30–60 cm vertically per day. Some species, such as Nereocystis, are annuals, while others such as Eisenia are perennials, living for more than 20 years. In perennial kelp forests, maximum growth rates occur during upwelling months (typically spring and summer) and die-backs correspond to reduced nutrient availability, shorter photoperiods, and increased storm frequency.