Pollution forms an invisible barrier for marine life

March 10, 2011
The sea star Patiria miniata. Credit: Photo by J. Puritz, HIMB/SOEST

Over 50 percent of the population in the United States and over 60 percent in the world live in coastal areas. Rapidly growing human populations near the ocean have massively altered coastal water ecosystems.

One of the most extensive human stressors is the discharge of chemicals and pollutants into the ocean. In the Southern California Bight, more than 60 sewage and urban runoff sources discharge over 1 billion gallons of liquid on a dry day with the two largest sources of contaminants being sewage from municipal treatment plants and urban runoff from highly modified river basins. These discharges transport large loads of known and unknown contaminants including , chlorinated hydrocarbons, petroleum hydrocarbons, nutrients, and bacteria, that have shown to be toxic to marine life, including both adult and larval (early development) stages. Most such as sea stars (starfish) do not move among locations as adults; instead juveniles swim in the plankton before settling onto the sea floor and growing into a sedentary adult. Despite the known toxicity of terrestrial discharge, no one had investigated if it is limiting dispersal of marine larvae between populations along urban coastal areas.

Researchers at the University of Hawaii at Manoa Institute of (HIMB) examined the genetic structure of a common, non-harvested sea star using a spatially explicit model to test whether the largest sewage discharge and urban runoff sources were affecting the genetic structure of this species. They found that these large pollution sources are not only increasing genetic differentiation between populations (presumably by limiting the dispersal of larvae between them) but also decreasing the of populations closest to them. In short, human beings are directly affecting the ecological and evolutionary trajectory of a species that is relatively free of any direct human impacts.

DNA sequences reveal patterns of dispersal in the larval stage of the life cycle. Credit: Image by M. Hart, HIMB/SOEST

UH Manoa PhD student Jon Puritz led the investigation, and when asked about the recent discovery said, "This study changes the scale at which we thought human beings can affect non-harvested marine species. These results have the potential to change the way anthropogenic factors are incorporated into marine reserve design and ecosystem-based management."

Co-author and HIMB assistant researcher Dr. Rob Toonen added, "This species was previously shown to have well-connected populations from Southern California to Southern Canada, but now we see that these urban runoff plumes in the Los Angeles area are a more significant hurdle for the microscopic larvae to cross than the remainder of the Pacific coast of the U.S."

Explore further: NASA Researchers Use Imaging Radar to Detect Coastal Pollution

More information: The full research report by Puritz and Toonen is published in the online journal Nature Communications available at: www.nature.com/ncomms/journal/v2/n3/full/ncomms1238.html

Related Stories

There's no scent like home

January 8, 2007

Tiny larval fish living among Australia's Great Barrier Reef spend the early days of their lives swept up in ocean currents that disperse them far from their places of birth. Given such a life history, one might assume that ...

New study ranks 'hotspots' of human impact on coastal areas

July 9, 2009

(Santa Barbara, Calif.) -- Coastal marine ecosystems are at risk worldwide as a result of human activities, according to scientists at UC Santa Barbara who have recently published a study in the Journal of Conservation Letters. ...

Recommended for you

A common mechanism for human and bird sound production

November 27, 2015

When birds and humans sing it sounds completely different, but now new research reported in the journal Nature Communications shows that the very same physical mechanisms are at play when a bird sings and a human speaks.

Study suggests fish can experience 'emotional fever'

November 25, 2015

(Phys.org)—A small team of researchers from the U.K. and Spain has found via lab study that at least one type of fish is capable of experiencing 'emotional fever,' which suggests it may qualify as a sentient being. In their ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.