'Caribbean Creep' chills out: climate change and marine invasive species

Abstract

Background: New marine invasions have been recorded in increasing numbers along the world's coasts due in part to the warming of the oceans and the ability of many invasive marine species to tolerate a broader thermal range than native species. Several marine invertebrate species have invaded the U.S. southern and mid-Atlantic coast from the Caribbean and this poleward range expansion has been termed 'Caribbean Creep'. While models have predicted the continued decline of global biodiversity over the next 100 years due to global climate change, few studies have examined the episodic impacts of prolonged cold events that could impact species range expansions.

Methodology/principal findings: A pronounced cold spell occurred in January 2010 in the U.S. southern and mid-Atlantic coast and resulted in the mortality of several terrestrial and marine species. To experimentally test whether cold-water temperatures may have caused the disappearance of one species of the 'Caribbean Creep' we exposed the non-native crab Petrolisthes armatus to different thermal treatments that mimicked abnormal and severe winter temperatures. Our findings indicate that Petrolisthes armatus cannot tolerate prolonged and extreme cold temperatures (4-6 °C) and suggest that aperiodic cold winters may be a critical 'reset' mechanism that will limit the range expansion of other 'Caribbean Creep' species.

Conclusions/significance: We suggest that temperature 'aberrations' such as 'cold snaps' are an important and overlooked part of climate change. These climate fluctuations should be accounted for in future studies and models, particularly with reference to introduced subtropical and tropical species and predictions of both rates of invasion and rates of unidirectional geographic expansion.

Figure 1. The green porcelain crab Petrolisthes armatus can be found in rock rubble or oyster reefs in shallow intertidal or subtidal areas.

It occurs in the western Atlantic (Gulf of Mexico, Bermuda, the West Indies and Caribbean, and South America to southern Brazil), eastern Atlantic (tropical western Africa and Ascension Island), and eastern Pacific (Gulf of California to Peru). Since the 1990s it has invaded the Mid-Atlantic (South Carolina to Florida).

Figure 2. Water surface temperatures (°C) from winter 2005–06 until winter 2009–10 at Fort Pulaski, Georgia (12 km from crab collection site).

Average daily temperatures (n = 24) from the National Data Buoy Center are indicated.

Figure 3. We exposed the invasive green porcelain crab Petrolisthes armatus to three experimental temperature ranges: constant 15°C (green); cold based on January 2010 temperatures: 5.3–14.4°C (blue); extreme: 4.1–11.7°C (red) for 25 days.

Water temperatures from the three treatments extracted with data loggers are shown.

Figure 4. Historical winter (120 days from December to March; n = 120) air temperature (°C) for 1958–2006 was collected at the University of Georgia Marine Institute on Sapelo Island, Georgia (65 km south of crab collection site).

Data from 2007–2010 are from the USGS Climate Station at Hudson Creek, Georgia (65 km south of collection site). Error bars represent the standard deviation of the mean.

Figure 5. Kaplan-Meyer survival curves of Petrolisthes armatus collected in Georgia and exposed to three thermal treatments.

Color codes as in Fig. 3. Dashed lines indicate 95% confidence intervals.