Yallop - Invasive species Flashcards
what is a beneficial species which was invasive to uk?
Elodea nuttallii
provides refugia and high BD
dirty dozen invasive species
- American signal crayfish
- Australian swamp stonecrop
- Chinese mitten crab
- Floating pennywort
- Giant hogweed
- Himalayan balsam
- Japanese knotweed
- Mink
- Red-eared terrapin
- Water fern
- Zander
- Zebra mussel
how has japanese knotweed become so successful in uk
Fallopia japonica
introduces mid 19C, grows on river banks
able to grow from tiny root fragments. roots colonise rapidly,seeds not viable in uk.
distribution doubled in 20 years in london. widespread on sides of pathways and derelict land.
authorities began treatment process at olympic park in 2007
why is it good to keep some japanese knotweed?
grows along banks of river, acting as buffer to erosion, but if there is too much of it, will reduce species richness and diversity.
how is japanese knotweed spread reduced?
Herbicides (mostly Glyphosate) and incineration
foliar appliction of herbicides, cut stump and stem injection (this is the only one likely to succeed).
uses the chychemate pathway to prevent growth.
disagreement over whether this actually works.
Why is JKW so difficult to treat?
extensive rhizome system is difficult to remove in entirety.
Biocontrol method of JKW
Aphalara itadori
sap sucking psyllid, introduced to try to reduce knotweed. however not species specific so may harm native species.
Females lay up to 600-700 eggs on plant surface in a life time
trials involving diff species of both knotweed and psyllid showed that both could reduce above and below ground biomass in 50 days
signal crayfish
ecology, biology and reason for rapid spread
- opportunistic polytroph
- Occupies same ecological niche as European noble crayfish and UK white clawed crayfish
- many impacts widely, prey for otter, snakes mink and fish, also good decomposer.
- native to N america, inteurope in 60s.
- carrier of crayfish plague, highly virulent to native crayfish
- 200-400 eggs laid per year
- sexually mature after 2 years, live up to 20 years. high fecundity is a reason for rapid spread.
experiment to quantify impact on fish community
Guan and Wiles 1997
found where high numbers of crayfish, low numbers of native fish such as bullhead, and stone loach.
artificial streams and shelters. intraspecific comp - only one in a shelter at a time. overall, most benthic fish were ousted from shelters by crayfish
compete for same food resources.
problems of signal crayfish
build tunnels into side of rivers for habitat. problems of erosion and drivers of fine sediment into river. mobile sediments present flood risk and risk of contaminant release.
Eradication options for invasive crayfish in gravel pit in Scotland
pesticides without removing native fauna is tricky but possible.
- Trial by Peay et al:
pyrethrum called Pyblast - non toxic to birds and mammals.
preliminary trials indicated appropriate doses for crayfish, no effect on native invertebrates e.g. Asellus (water hog-louse) or Gammarus (water shrimp).
affected mainly juveniles in field exp.
- deoxygenation with sodium sulphite tried to oust crayfish from burrow but not successful as interfered with pesticide action.
- instead categorised behaviour to measure effectiveness of pesticide.
lacked several years of follow up monitoring.
Current Measures to eradicate species
Strict Legislation
Trapping
Pesticides - many illegal and non selective
Electro-fishing - time consuming
Pheromones - good for catching but doesnt eradicate.
Weirs
no method trialled was successful in controlling signal crayfish, pops continure to expand. need to destroy all individuals
impacts of derissena polymorpha
zebra mussel
Dreissena polymorpha
can clear turbid water, too many can drive system from pelagic to benthic and limit size of food chains
pos and neg impacts
Zebra Mussel: Biology
origin, SE russia
transported by cargo ships to N america, britain and europe.
5cm max size. filter feeder causes habitat alteration.
4-5 year life cycle, spawns at 2 years old. many eggs, poor dev to adult stages.
treatment of zebra mussels
also 2 examples
early detection necessary Successful eradication achieved using: Oxidising chemicals Heat treatment Larvae targeted biocides
eg Lake George NY - Manual removal by SCUBA divers
860 dive hours
Depended heavily on volunteers
Low calcium conditions
eg Milbrook quarry, Virginia
Pumping potassium chloride (KCl) solution into the water
Lethal for zebra mussels, but not other non-molluscan biota
spread of American mink through UK
1920s - introduced for use in fur trade. escaped and increasing pop of feral mink
1950s - confirmed to be breeding in uk
current - distributed throughout england, wales and most of scotland.
causes decreased biodiversity, impact on native species, particularly water vole and ground nesting birds.
example of an invasive species with benefits so cases of it considered desireable
zebra mussel
ecosystem engineers
‘Benthification’
filter phytoplankton so if shallow, more clarity and promotes macrophyte growth.
what are 5 possible positive advantages of Invasive bivalves?
Provide Shelter Substrate for colonisers Rework sediments Filter feed Increase light penetration
what is a common approach of removing invasive species?
apply pesticides, insecticides or herbicides
this is damaging if thy dont break down, or if they decompose into something more harmful.
many toxicants have been detected in FW
difficult to monitor pesticides in water, very few water bodies are regularly monitored.
what was found by Brown et al 2006, in study of agriculture and FW bodies?
National-level risk mapping
Crop type major driver for potential risk to the aquatic environment from agricultural use of pesticides.
Orchards were identified as the crop type associated with the greatest potential risk.
Cereals, oilseeds, potatoes and vegetables were found to be an order of magnitude smaller in risk than orchards.
water bodies near an orchard were all impaired, many almost monoculture of Gammarus.
what is another source of pesticides in water bodies aside from agriculture ad industrial sources?
eg lindane conc correlated well with pop density in rivers surrounding Lough Neagh, ireland. source linked to use of wood preservatives in homes. affected mayfly survival.
How are we currently testing for impacts of new toxicants?
ISO
OECD
ISO - International Organsiation for Standardisation - independant, non governmental membership org. Develops voluntary international standards.
eg reccomends standard test organisms:
algae: Navicula pelliculosa 104 cells/ml
cyano: Anabaena flos aquae 104 cells/ml
clones are available to buy, grown under same conditions.
OECD (Organisation for the economic Cooperation and Development) test, has strict guidelines. - standard growth test - measure growth rate in 72 hours under defined conditions. exposed to test substance. EC50 calulated defining conc bringing about 50% reduction in growth.
describe toxicity test on Daphnia magna
Young female Daphnia, aged up to 24 hours are exposed to the test sample at a range of concentrations over the set time period.
After, the total number of living offspring produced per parent individual alive at the end of the test is assessed.
for toxicity testing of a pesticide, must obtain EC values of a range of orgs, including an alga, invert and vertebrate. only 3 species of fish approved for this.
why is it not a good idea to continually apply pesticides to lakes?
cumulative poisoning :
Eg. Clear Lake, California. Insecticide used to remove midges that caused problems for tourism- ultimately led to death of thousands of grebes following bioaccumulation
what is an overused herbicide in the US>
Atrazine - used to treat broadleaf weeds in corn and sorghum fields.
good records of use in US by US Geological Survey.
surface waters surveys - 55% of basins exceeded US Environmental Protection agency maximum contaminant level for atrazine.
Invasion of Zebra mussel and impacts
catastrophic effects of zebra mussel in Laurentian great lakes 1980s, great threat to ecosystem. larvae survive a long time, and bysall threads enable attachment to substrate.
Side scan sonar revealed presence of extensive zebra mussel beds on soft sediments in lake erie.
positive impacts - increased water clarity so macrophytes established
neg impacts - major biofouler, blocking raw water cooling systems of powerstations and water treatment works costing $1-5billion annually.
novel biocontrol method for zebra mussel
Molloy et al 2013
used pseudomonas fluorescens strain CL145A,
cell walls release substance toxic to mussels epithelial gut cells.
Species specific although unsure why. Biotoxin likely to be a secondary metabolite.
toxicity test for pesticide for zebra mussel
Zequanox - novel biocide in selected non irish aquatic species.
72 hr static toxicity tests
Chironomus plumosus, non biting midge, 28% mortality at 72h.
Austropotamobilus pallipes - white clawed crayfish - low mortality.
good alternative to pesticides for zebra mussel
chlorination didnt work - mussels sense chlorine and close valves for 3 weeks . Cl in water produces trihalomethanes (THMs) by reaction with organic matter, which is toxic to other orgs.
Instead used microencapsulated Biobullets with KCl crystal inside vegetable oil matrix. Aldridge et al 2006.
Food based coating so mussels ingest it and takes a few hours to leach into org. 68% mortality at 24 and 48h.
