Lecture 5: Invasive Species

Lecture 5: Invasive Species

Lecture 5: Invasive Species

What is an Invasive Species?Exotic species vs. invasive species

Why are Invasive Species Problematic?Alteration of habitatChange in the diversity, abundance, and distribution of members of the preexisting natural communitiesCompetition with native speciesBroad and cascading effects throughout communities and ecosystems

Vectors for Introduction in Marine Environment1. Ocean-going ships, exploratory petroleum platformsBallast water, fouling organisms

Vectors for Introduction in Marine Environment2. Canals

Vectors for Introduction in Marine Environment3. Mariculture (Aquaculture)

Vectors for Introduction in Marine Environment4. Saltwater Aquarium/Pet Industry

Vectors for Introduction in Marine Environment5. Saltwater Bait Industry

Vectors for Introduction in Marine Environment6. Marine and Maritime Plant Community Restoration/Erosion Control

Vectors for Introduction in Marine Environment7. Scientific Research/Education

Need more here14Where do invasions occur?Deep sea benthic habitatsContinental shelf pelagic habitatsContinental shelf sublittoral benthic habitatsContinental shelf sublittoral kelp bedsIntertidal zoneRocky shoresSandy beachesSoft sediment shores

Where do invasions occur?Coral reefsEstuariesMangrovesSalt marshesSupralittoral fringe

Habitat Alteration

PollutionClimate Change

Fisheries Impacts

Introduced Species

Changes in Trade Routes/Petroleum Exploration

Changes in Patterns of Fisheries and Mariculture

Increased Numbers of Recreational CraftBIOINVASIONSAdapted from Norse and Crowder 2005, Fig 8.1

Challenges with Understanding Invasive Species1. Strong historical biases in the invasion record

2. Limitations of taxonomy; cryptic invaders

3. Decline in the study of marine invertebrates and algaeCase Study: San Francisco BayConsidered to be one of the most invaded aquatic regions in the world

More than 7,000 container ships transit the Bay every year. Scientists estimate that approximately one new exotic species comes to the San Francisco Bay every 14 weeks, so it is no surprise that the Bay is home to 240 invasive species comprising 97% of the total number of Bay organisms.20

www.exoticsguide.orgCorbula amurensis

Caulerpa taxifolia

www.sfgate.com

Carcinus maenaswdfw.wa.gov

http://www.bsu.edu

www.spartina.orgThe pervasive overbite clam, Corbula amurensis, is suspected to have entered the San Francisco Bay as larvae discharged with a ships ballast water. Now the tiny clam can be found in huge numbers 19,000 clams per square meter in some regions of the Bay. Because it can tolerate a variety of temperature and salinity conditions, it has truly thrived, to the detriment of the Bay. The invasive clam consumes phytoplankton at a rapid rate and limits the base of the food web, making San Francisco Bay a less productive ecosystem. It also assimilates contaminants in the water more readily than other clam species. As a result, the clams themselves actually become toxic and can poison the fish and ducks that feed on them.The best way to protect the Bay from the damage of more invasive species is to regulate the ships that carry them. In July 2008, San Francisco Baykeeper won a legal victory to prevent the spread of invasive species in our waterways. The U.S. Court of Appeals for the Ninth Circuit ruled that the U.S. Environmental Protection Agency (EPA) must regulate ship discharges, including ballast water discharges containing invasive species, that pollute U.S. waters under the Clean Water Act.Caleurpa taxifolia Forms a dense, smotheringblanket that kills otherunderwater vegetation; has novalue for fish, birds or wildlife,so creates underwaterwastelands22Invasive Lionfish

www.divingdr.comPterois volitans; Pterois milesUp to 18 longAmbush predators

daniellesdives.wordpress.comSpread of Lionfish

Potential future range of lionfish based on the lethal thermal minimum of 10C (Morris J.A. 2009).24

Shows a healthy food chain (left) versus one with fishing pressure and introduced lionfish, demonstrating the negative impact lionfish indirectly have on corals. Size of the organism indicates relative abundance and thickness of the arrow shows relative strength of the interaction. Solid arrows are direct effects and dashed arrows are indirect effects. Image taken from: Albins, M. A. and M. A. Hixon. 2011. Worst case scenario: potential long-term effects of invasive predatory lionfish (Pterois volitans) on Atlantic and Caribbean coral-reef communities. Environmental Biology of Fishes:1-7speakupforblue.comAs far as their effect on the reefs one of their prey targets are a family of fishes known as parrotfish. One of the major ecosystem functions of parrotfish is feeding on algae that otherwise outcompetes corals and in some areas where parrotfish and other herbivores are largely absent have led to a phase shift to an algal dominated ecosystem which provides very little habitat for juvenile fishes to shelter from predators among other things. By reducing the number of parrotfish on the reefs there is the potential for the lionfish to have further ramifications on the reefs by releasing the algae to outcompete the coral for space on the reef.25

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