Invasive species

1. MR 608: MARINE CONSERVATION SCIENCE
Lecturer: Dr. Chauka
Samira Ahmed Khatib
Ibrahim Mgata
Thomas Becker Paschal

2. Definitions
• Some terms are used interchangeably, such as nuisance and invasive, both with
a negative connotation. Four categories serve to cover the concepts used to
describe the status and the distribution of a particular species.
– Native, Indigenous: species naturally occurring or originating in a
geographical region since prehistorical time
– Introduced, Alien, Exotic: deliberate or accidental release of a species into an
area in which it has not occurred in historical times
– Invasive: the establishment of self-regenerating and spreading populations of
a naturalized species in a free-living state in the wild, takes possession and
may affect injuriously
– Nuisance, Noxious, Weed: any plant, either native or introduced, with a
harmful or destructive influence on existing natural communities, interfering
with the objectives or requirements of people

3. How Do Invasive Aquatic Species Travel?
Allien Invasive Species can travel by
•Stocking
•Shipping
•Aquarium Release
•Bait Release
•Aquaculture
•Canals
•Pet Escape

4. Why are Allien invasive species so successful?
Invasive plant species often lack natural predators, diseases, and other
pathogens that keep them in check in their native habitats.
They have competitive adaptations including
• aggressive reproductive strategies, and
• efficient dispersal methods.
In many cases, they take advantage of disturbances and establish
themselves before native species can get a foothold.

5. What takes a particular specie to become an allien
invasive specie
• It should adapt to the area easily and quickly
• It must reproduce very quickly
• It must cause harm to the economy, Or native plants and animals of
the region

6. Examples of alien invasive species in marine ecosystem
(a)The lionfish (Pterois miles)
is widely spread in the
Mediterranean and Caribbean
Seas, and Western Atlantic
(b)The orange cup coral
(Tubastraea coccinea) is a
highly spread in the invaded
regions of Brazil, the Gulf of
Mexico, and the Caribbean Sea
(c)The killer alga (Caulerpa
taxifolia), has high dispersion
capacity but was successfully
eradicated in California
(d)The upside-down jellyfish
Cassiopea andromeda

7. Effects of alien Invasive Species in marine Ecosystem
Impact on Ecosystem services
• Food provision
Phytoplanktonic invasive species may bloom, causing damage to aquaculture or
fisheries.
 Alexandrium minutum has caused persistent blooms in northern Europe since
1985, causing severe economic losses to aquaculture.
 Alien species such as the macroalgae Acrothamnion preissii, Caulerpa
cylindracea, C. taxifolia, Codium fragile subsp. fragile, Gracilaria vermiculophylla,
Lophocladia lallemandii cause the degradation of important biotopes, which
support stocks of commercial and non-commercial fish

8. Effects of alien Invasive Species in marine Ecosystem
Impact on ecosystem services
• Coastal protection
Important habitats for coastal protection include biogenic reefs (e.g. oyster and
mussel reefs), kelp beds, and seagrass meadows
Alien species that cause the degradation of such habitats (e.g. Acrothamnion
preissii, Gracilaria vermiculophylla, Lophocladia lallemandii, Womersleyella
setacea) can have a severe negative impact on coastal protection
However the same species may trap sediments (i.e., have a positive impact).

9. Impact on ecosystem services
Water purification
Many alien species may have a negative impact on water purification by causing
the degradation of important communities and their habitats that provide such a
service, such as those of sublittoral algae, seagrasses, and mussel or oyster reefs.
E.g the gastropod Rapana venosa, and the fish Siganus luridus and S. rivulatus. R.
venosa is responsible (through predation)
Effects of alien Invasive Species in marine Ecosystem

10. Impacts on ecosystem services
Climate regulation
CO2 dissolved in saltwater forms carbonic acid, the anion of which (carbonate) is
used by shelled mollusks and corals to make calcium carbonate skeletons or
shells and by algae to strengthen their cell walls against grazers.
Hence, alien species that create such skeletons or shells have a potentially
positive impact on carbon sequestration and thus on climate regulation.
All the alien shelled mollusks that develop massive populations, increasing the
overall mass of calcium carbonate, have a positive impact on climate regulation.
Effects of alien Invasive Species in marine Ecosystem

11. Control measures towards invasive alien
species
By ‘control’, “we refer to the reduction of the population to
such levels that their ecological impacts are substantially
mitigated”
Control measures towards invasive alien species

12. Control measures towards invasive alien species
Physically (mechanically) remove the species.
Rehabilitate the environment (e.g. protect and/or restore marine areas).
Encourage the targeted removal and commercial and/or recreational utilization
of dead specimens (trading live specimens for use in aquaria is not included).
Deploy biocides in the sea, tactically applied.
Promote native consumers (predators or grazers) that feed on the invasive
species (e.g. by restocking predator populations).

13. Encourage native diseases and/or parasites that affect the invasive population.
Apply biological control, using alien parasites and/or diseases.
Apply biological control, using alien consumers (predators or grazers).
Apply genetic approaches that affect only the invasive.
Education and public awareness.
Do nothing.
Control measures towards invasive alien species