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!