Algal Turf Takeover

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Filamentous seaweeds

Key Points:

  • Algal turfs are thick, carpet-like beds of seaweed that retain sediment and compete with foundation species like corals and kelps.
  • High nutrient and sediment loads in urban waters may be facilitating the expansion of algal turfs.

Are algal turfs taking over the marine environments as a result of widespread urbanization? That’s the worry of scientists who study marine macroalgae. Algal turfs are expansive beds of sediment-retaining seaweeds, and are common features of urban areas. They have long been black listed by conservationists and many ecologists because they compete directly with reef-building corals and perhaps also canopy-forming kelps, both taxonomic groups of considerable importance for marine biodiversity.

Though the term ‘algal turfs’ is used to refer to a variety of different types seaweeds, those in urban areas are typically formed by filamentous algae that are just a few centimeters tall and grow in dense, intertwined matrices or ‘thickets’. Urban algal turfs are thought to consist of opportunistic, pioneer species capable of colonizing novel habitats rapidly and tolerating of stressful environmental conditions that are inhospitable to other organisms. In particular, urban turfs appear to thrive on elevated nutrient levels (primarily nitrogen and phosphorous from wastewater, sewage, and runoff) and high sediment loads (from coastal construction, dredging, and other sources). Recent studies also suggest urban turfs may be further facilitated by increases in temperature and CO2 associated with climate change. Currently, researchers are working to understand how herbivores and competitors that limit algal turf may be used to control turf growth in urban areas.