Research Summary: Some Like it Sour: Effects of Ocean Acidification and Other Stressors on Growth Rates of an Invasive Red Alga
Summary written by Aly Putnam, edited by Jordanna Barley
Summary
The effects of climate change have facilitated the introduction and range expansion of invasive species in coastal marine environments. Other anthropogenic stressors, such as eutrophication, caused by excessive nutrient runoff into coastal waters, can further the establishment and population growth of marine invasive species. Several species of marine macroalgae have become invasive to the western Atlantic region and benefit from the effects of anthropogenic and climate change stressors. Native to the western Pacific Ocean, Dasysiphonia japonica is a filamentous tube forming red macroalgae which has dominated European coastlines and most recently Southern New England and the Gulf of Maine (2007, 2012 respectively). D. japonica is capable of altering algal communities from multidimensional to short turf, grows epiphytically on and negatively impacts important foundational species such as kelp and seagrass, and can overgrow shellfish (oyster) beds. Through a series of laboratory experiments, Young and Gobler (2021) assessed the effects of climate change (ocean acidification: elevated pCO2 and temperature) and other anthropogenic stressors (elevated nutrients: nitrate and phosphate) on the growth rates of D. japonica to better understand the conditions that facilitate the success of this invasive species. Their results show that the growth rate of D. japonica was significantly enhanced during experiments in elevated pCO2 and nutrients that were at or below 15C, while the growth rate was significantly increased by nutrients alone at a broad temperature range (4-23°C). Growth rates of D. japonica were also greater than those of native macroalgal species used in this experiment. Surveys in the Long Island region demonstrate a seasonal variation in the abundance of D. japonica tracking patterns of pH (pCO2) which were low in colder months and higher in warmer months. The authors suggest elevated levels of pCO2 (ocean acidification) and nutrients to be driving factors of this species' successful invasion.
Take home points
Growth of D. japonica increases when exposed to elevated pCO2 and excessive nutrients (nitrate and phosphate) in a laboratory setting, more than double that of native red macroalgal species used in trials
In the natural environment, eutrophication can promote seasonal fluctuations in pCO2 which can drive seasonal changes of D. japonica
Although previously thought to be a cold-water species with optimal growth between 19-25°C, D. japonica has shown a broad range of tolerance to temperature (0-30°C) and a broad temperature range for growth (4-24°C)
Management implications
Estuaries and coastal ecosystems with maximum annual temperatures of < 28°C may be more at risk to invasion of D. japonica
Foundational and economically important species such as kelp, seagrass, and shellfish species can be negatively impacted by overgrowth of D. japonica
Management and reduction of nutrients added to marine waters would aid in the conservation of coastal regions to D. japonica establishment and overgrowth
Movement of marine vessels (shipping, recreational and commercial boating activities, and aquaculture trade) has been identified as a major source of invasive species introductions. Management of this sector tends to be the most effective strategy for preventing the introduction and limiting the spread of D. japonica
Keywords
Dasysiphonia japonica, Southern New England, Ocean acidification, Eutrophication, Climate extremes