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J E N N I F E R E . S M I T H
S C R I P P S I N S T I T U T I O N O F O C E A N O G R A P H Y
N A T I O N A L I N V A S I V E S P E C I E S A W A R E N E S S W E E K
Invasive Marine Algae in Tropical and Temperate Seas & Implications for
Climate Change
Outline of Talk
Overview
Species of concern
Impacts of invasive algae
Vectors of introduction
Climate impacts likely to affect invasive algae
Challenges and strategies for the future
•One of the largest threats to global biodiversity-better competitors than native species•Large economic impacts-tourism, fisheries, mitigation, clean-up, eradication•Habitat destruction-ecosystem engineers•Alterations in productivity & trophic dynamics-cascading effects of invaders on food web
Impacts of Marine Invaders
Overview of Invasive Seaweeds
407 separate introduction events documented
277 total species of “introduced” marine algae identified
Many more cryptic species
Majority of introductions have occurred in temperate seas (< 25% in the tropics)
While many are considered “invasive” only 17 species or 6 % have been studied for impact assessment
Large impacts documented for seaweed invaders in both tropical & temperate regions
TEMPERATE INVADERS
Caulerpa taxifolia
Undaria pinnatifida
Codium fragile
Sargassum muticum
TROPICAL INVADERS
Gracilaria salicornia
Hypnea musciformis
Acanthophora spicifera
Eucheuma denticulatum
What do we know about the impacts of invasive seaweeds in marine communities???
• Reviewed 68 studies (> 900 reviewed)• Most observational • Only 17 out of 277 introduced species have been examined to determine impacts• 40 % of studies showed negative impacts of invaders
Williams and Smith (2007) Annual Review of Ecology, Evolution & Systematics
Impacts of Seaweed Invaders on Communities
Williams and Smith (2007) Annual Review of Ecology, Evolution & Systematics
Invasive Seaweed Impacts
Most common impacts are reductions in native species abundances, native species diversity and native species performance (growth, reproduction, etc) as well as changes to community structure
The majority of impacts are negative however positive effects on the have also been documented
Williams and Smith (2007) Annual Review of Ecology, Evolution & Systematics
What do we know about the vectors of introduction for invasive seaweeds???
• Total of 407 invasion events identified in the literature• 277 total species• Vectors noted for only 60 % of the introduction events
Williams and Smith (2007) Annual Review of Ecology, Evolution & Systematics
Vectors of Introduction for Invasive Seaweeds
Williams and Smith (2007) Annual Review of Ecology, Evolution & Systematics
How might climate change affect non-native invasive seaweeds?
Climate Change Factors Likely to Affect Invasive Marine Algae
Increase in ocean temperatures
Change in ocean circulation and currents
Change in habitat as caused by rising sea level
Ocean acidification
Increases in Sea Temperature
Many regions have already experienced warming of coastal waters Alterations in species ranges
Expansion of species tolerant to warm waters-migrating pole-ward
Reduction in ranges of cold water species-shrinking pole-ward
Alteration in the timing and/or extent of reproduction
Some temperate invasive algae have been noted to become less seasonal and are now reproducing all year round whereas in their native ranges they have much stronger seasonality
Tropical or subtropical species (warm water adapted) may be more likely to invade in temperate with warming waters
Tropical algae have already successfully invaded temperate locations and these tropical-to-temperate algal invasions may become more common
Tropical to Temperate Invasions
Caulerpa is a tropical algal genus
Cold-water tolerant strain has become highly successful
With warming this species, other members of the genus &/or other species altogether may invade other temperate locations
Warming Waters in the Tropics
Corals bleach as a result of increased water temperatures-often resulting in death
Dead coral=suitable habitat for seaweed species
Coral to algal phase shifts
Fast growing invasive seaweeds may be become more abundant as coral bleaching increases
Changes in Circulation & Current Patterns
Climate change is expected to alter ocean currents
Affect ranges of native and invasive species
May facilitate spread of pre-existing invaders into new locations
May cause local extinctions
Sea Level Rise
With rising sea level
More submerged habitat available for colonization by marine species
Habitat will be highly disturbed and in many cases man-made; native species may not be adapted
High levels of sedimentation and pollution-eutrophication
Likely to promote “weedy”, fast growing invasive species
Ocean Acidification
Increases in dissolved CO2 in ocean-reduced pH-reduced carbonate saturation state-more difficult for organisms to “calcify”
Corals and other coralline algae may be significantly threatened; data suggest reduced growth
May strongly favor communities dominated by fleshy species All tropical invasive algae are fleshy/non-calcified spp. and
may become more successful as calcifiers are lost from system Cascading impacts
Ocean Acidification
Implications: Loss of corals and coralline algae: loss of reef builders=loss of habitat
Coralline algae facilitate settlement of many invertebrates (both tropical and temperate)-loss of species that depend on cues
Loss of other calcified algae-Halimeda-forms up to 90% of the sand in the tropics-loss of sand production
Loss of carbonate accretion-community likely to be dominated by fleshy algae
Control
High CO2
Future Needs & Strategies
More partnerships between federal agencies and academic institutions to build capacity to detect, respond and manage invasive species
Basic research to determine the response of invasive seaweeds to climate impacts and interactions of local and global stressors
Need to build predictive models-niche models, etc.
Risk assessment and prioritize species that deserve rapid responses
National strategy for monitoring & research
Thank You Celia Smith, Peg Brady, NOAA and all of you!