EVSC20004 Lecture 27: Community change
21 Jun 2018
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Community change: Introduced marine species
Definitions:
Introduced: Species transported by human activities into regions in which they did
not occur in historical time and are now reproducing in the wild; not native to the
area
Cryptogenic: Species not demonstrably native or introduced
Invasive: Species that spread from their point of introduction and cause
environmental damage
Weed: Plant growing in an area where it is not wanted
Pest: Organism considered harmful to human activities (including plants)
Port Phillip Bay is known as one of the world’s most invaded marine systems:
99 introduced (2003- and another one introduced in 2010)
61 cryptogenic (2 more possible introduced by 2010)
Some of the most unwanted species at Port Phillip Bay are:
Norther Pacific sea star
Green alga
Polychaete worm
Brown alga
Human-mediated biological invasions pose a major threat to native biodiversity- they
present a threat to habitats and ecosystem function (Displaces native species, remove
larvae of native species, change how the water column works). In addition, they create
economic impacts.
Impacts of the Northern Pacific Seastar (Asterias amurensis):
Voracious predator
Cause damages to commercial shellfish including oysters, cockles and scallops via its
stomach
Impacts of the green alga (Caulerpa taxifolia):
Has toxins inside it, can cause damage to fish assemblages (Reduced commercial fish
catches)
Entangles nets and boat propellers
Create large monospecific meadows
Impacts of comb jelly (Mnemiopsis ledyi):
Found its way to the Black Sea introduced by ballast water.
Fills the water column- clogs nets, kills off fish (feeds on fish eggs and larvae)
Not good in big numbers
There is a National Introduced Marine Pest Information System that covers the different
species declared as pests- at least 50% are found in Port Phillip Bay.
find more resources at oneclass.com
find more resources at oneclass.com
There are some introduced species that aren’t actually pests (Therefore, not all introduced
species are pests to native flora and fauna)- e.g. Red alga (Deucalion levringii) and Hydroids
(Antennella secundaria).
The process of invasion:
1) Species present in donor location
2) Hitches ride with vector and survive the journey to the new location (typically a port)
3) Is released/ escapes into recipient location
4) Survives in recipient location
5) Establishes in recipient location (self-sustaining population)
‘10s Rule’- Only about 1 in 10 of hitchhiker species make it at each step from the second
step. Therefore, only 1 in 1000 only impact native assemblages (only 1 in 1000 become
pests).
Potential vectors:
International shipping:
oFouling (Organisms stuck to the outside of a vessel and transported)
Hull, sea chests etc.
This is the highest contributing vector in Australia
oBallast (Full of larvae, eggs etc.)
oAquaculture (Known vector)
Deliberate introductions- Pacific oyster to Tasmania, Vic, SA, WA
(outgrows Sydney rock oyster), Undaria to Atlantic coast of France
1983
Accidental introductions- Herpes virus possibly with imported feed
stock for sea-caged tuna, Undaria to Mediterranean in 1971 probably
on oysters
oAquarium trade
oDomestic shipping
oCommercial fishing
oRecreational boating
*Anchor used in different waters without being cleaned
Other vectors include the packing for live bait, miscellaneous maritime activities (e.g.
construction, drifting infrastructures).
o165 tonne dock washed ashore in Oregon, USA- drifted across Pacific Ocean
after being torn loose from Japan during 2011 tsunami. It brought with it
Japanese-native flora and fauna into the US.
People who are concerned about invasion of introduced species are also concerned by
propagule pressure (zygotes, eggs, etc.). For each arrival event (passage of a vessel,
dropping of anchor from a recreational event), the number of propagules introduced share
a relationship with the probability that they will become pests.
There are 2 types of propagule pressure:
find more resources at oneclass.com
find more resources at oneclass.com
1) Consistent marginal benefit- Refers to the linear relationship between propagule
pressure and probability of establishment (The higher the propagules introduced,
the higher the probability of establishment)
2) Redundant past threshold- Refers to the relationship wherein once a propagule is
introduced, its establishment occurs quickly and then reaches a maximum
In understanding these 2 different types of propagule pressure, we can figure out how to
regulate these propagules in relation to their impact on the environment- for consistent
marginal benefit, we can revolve regulation around preventing further propagule impact;
for consistent marginal benefit, we can determine that any additional management is a lost
cause because the damage is already done.
What makes a successful invader?
Short life cycle
Rapid growth
Early onset of reproduction
High fecundity
Ability to colonise new/disturbed substrates
Disturbance and invasion:
Disturbed environments may be prone to invasion (Less ability to withstand with the new
pressure)
E.g. Undaria pinnatifida displacing native species on cleared substrate (Not good at
invading area full of healthy like-species), and encrusting bryozoans tolerant of
toxicants (Their ability to withstand contaminants makes them well suited to invade
an area where the native species can’t deal with their polluted environment)
Types of invaders:
Trackers are introduced species that can establish when there has been some impact
on the native assemblage to allow it to get in there (undaria)
Drivers can make their own way to an assemblage (Don’t need a disturbance, can
just enter the environment- make their own opportunities)
Management approaches:
Eradication of established pests are very difficult as it can cost a lot and cost the loss
of native area to native flora and fauna. It is easier to eradicate established pests in
confined areas (Remove by hand or mass clearing of pests)
If you can’t eradicate, you can control established populations (keep the numbers
down)
Prevention of pest arrival is the best option:
oAntifouling coatings
oBallast water management
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Introduced: species transported by human activities into regions in which they did not occur in historical time and are now reproducing in the wild; not native to the area. Invasive: species that spread from their point of introduction and cause environmental damage. Weed: plant growing in an area where it is not wanted. Pest: organism considered harmful to human activities (including plants) Port phillip bay is known as one of the world"s most invaded marine systems: 99 introduced (2003- and another one introduced in 2010) 61 cryptogenic (2 more possible introduced by 2010) Some of the most unwanted species at port phillip bay are: Human-mediated biological invasions pose a major threat to native biodiversity- they present a threat to habitats and ecosystem function (displaces native species, remove larvae of native species, change how the water column works). Impacts of the northern pacific seastar (asterias amurensis): Cause damages to commercial shellfish including oysters, cockles and scallops via its stomach.
