Down but not out: Recovery and growth differences between native and non-native marine algae

Kraemer, G., Yarish, C., Kim, J. K., Zhang, H., & Lin, S. (2017). Life history interactions between the red algae Chondrus crispus (Gigartinales) and Grateloupia turuturu (Halymeniales) in a changing global environment. Phycologia, 56(2), 176-185. https://doi.org/10.2216/16-72.1

Written by: Annette Evans, Reviewed by Aly Putnam

Summary 

Coastal marine ecosystems experience widespread and frequent introductions of non-native taxa, such as seaweeds and algae, due to high densities of marine ports and marine traffic. Physical disturbances, like hurricanes, can further influence these systems by altering competitive interactions in the intertidal zone through substrate disruption, species mortality, and shifts in resource availability such as nutrients, space, and light. But the extent to which these disturbances preferentially facilitate the establishment and spread of non-native taxa remains uncertain, as their impacts on native and non-native species can vary. Therefore, large storm events and other climate-related disturbances (e.g., changes in water temperature) may play a critical role in reshaping competitive dynamics and facilitate the persistence and spread of non-native taxa.

In Long Island Sound, the lower intertidal zone is dominated by native seaweed Chondrus crispus and non-native red alga Grateloupia turuturu. After Hurricane Barry (June 2007), their combined cover dropped from 35% to <1% cover thanks to physical substrate disturbance by storm waves. Surveys by Kraemer et al. showed that within four months, G. turuturu rebounded rapidly, while the cover of C. crispus recovered more slowly. Although C. crispus remained dominant the intertidal community overall and has strong dispersal capabilities, growth chamber experiments revealed that post-germination growth of G. turuturu was faster than C. crispus under warmer temperatures (44–98% faster growth at 15–25°C), and also outpaced C. crispus across salinity (50% increase in growth) and light (70% increase) conditions.

With water temperatures in Long Island Sound already rising ~0.4°C per decade from 1979 to 2002 and storms expected to intensify with climate change, competitive dynamics between these two algal species may shift, potentially allowing the non-native alga to spread and impact larger marine areas across the northeastern U.S. coast.

Take Home Points 

●      Climate change is altering extreme weather events, such as hurricanes, as well as ambient ecological conditions, which can impact the introduction, establishment, and spread of non-native taxa.

●      The lower intertidal zone of Long Island Sound in Connecticut is dominated by native Chondrus crispus algae, which create complex habitat for marine invertebrates. This native alga competes with the non-native red algae Grateloupia turuturu, which differs in life history traits such as growth rate and environmental tolerances.

●      In 2007, Hurricane Barry reduced the combined cover of these two algal species from 35% to <1% thanks to physical disturbance of the substrate these algae attach to. In the months that followed, non-native algae G. turuturu recovered faster than native C. crispus, although the native algae did eventually return to pre-storm relative cover densities.

●      Growth chamber experiments revealed G. turuturu growth rates were faster than C. crispus across multiple temperature, salinity, and light regimes, highlighting life-history characteristics that may be beneficial to this non-native algal species.

●      Climate change is likely to increase the severity and frequency of extreme storm events, and raise water temperatures in Long Island Sound, which may expand the range and the negative effects of non-native G. turuturu, although C. crispus does show strong dispersal capabilities.  

Management Implications

●      Extreme weather events, such as hurricanes, can alter the distribution, cover, and ecological dynamics of both native and non-native species. Collecting baseline data on both native and non-native species prior to large storm events can provide important insights into how storms may differentially affect species.

●      Species that are severely affected by storm events may still recover to post-storm densities in the long term, although recovery is dependent on the specific ecological interactions between species from the same trophic level.

●      Many non-native species have life history characteristics (e.g. growth rate, broad environmental tolerances) that may convey an adaptive advantage under climate change. Identifying which species are likely to expand their range or enlarge their impacts will be critical for prioritizing species for early detection and rapid response, particularly in aquatic environments where detection and management is challenging.

Related Papers

This research summary is part of a series on the link between hurricanes and invasive species. For other research summaries on this topic see: Falk et al. 2024, Bhattarai and Cronin, 2014, and Colleran and Goodall, 2014. For the Research-to-Practice paper (R2P2) on this topic see: Rock you like a hurricane: The perfect storm for an invasion.

Keywords 

●      Climate extremes

●      Range expansion

●      Changing biotic interactions (competitiveness)

●      Chondrus crispus

●      Grateloupia turuturu

●      Long Island Sound

●      Connecticut

●      Macroalgal species richness

●      Hurricane