Transcript Ecological Management factors associated with Wind Farms

Ecological Management factors
associated with Wind Farms, Oil
Rigs and other Off-Shore Marine
Structures;
all serviced by large vessels.
Introduction: WINDFARMS
• Wind power is growing at the rate of 30% annually, with a
worldwide installed capacity of 121,000 megawatts (MW)
in 2008, and is widely used in European countries and the
United States.
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Wind Farm Types
Onshore
Offshore and Nearshore
Offshore wind farms are generally considered to be ten
kilometres or more from land.
• Nearshore wind farms are on land within three kilometres
from the coastline or on water within ten kilometres of
land.
Transition piece and foundations (under water)
require a Cathodic Protection (CP)design system (sacrificial
anodes) and a paint system.
Corrosion: ALL OFF-SHORE MARINE STRUCTURES (INCLUDING WIND FARMS)
• Greater problem of access during bad weather, and greater expense when
replacing larger main components. Transition piece, foundations etc
require a Cathodic Protection (CP)design system (sacrificial anodes) and a
paint system.
• Galvanic or sacrificial anodes are designed with a more negative
electrochemical potential than the metal of the structure. The voltage
potential of the steel surface is polarised (pushed) more negative until the
surface of the structure has a uniform voltage potential and the driving
force for the corrosion reaction is halted. The sacrificial anode continues
to corrode (sacrifice), which consumes the anode material until it requires
replacement. The polarisation is caused by the current flow from the
anode to the cathode. The driving force for the CP current flow is the
difference in electrochemical voltage potential between the anode and
the cathode.
• Galvanising (also known as Hot Dip Galvanising) is the process of applying
a zinc coating to steelwork which prevents corrosion of the protected
metal by forming a protective physical barrier.
• Benefits: Protection - Coverage - Coating toughness
Protecting against Marine Biofouling
• Marine fouling and biofouling can form on structures at all depths and
temperatures and is commonly found in vessel's seawater cooling systems.
• A common Anti-fouling system consists of two types of
anodes, a Copper alloy rod to prevent fouling and Aluminium
or Ferrous alloy rod to prevent corrosion.
• An anti-fouling anode, once fitting requires little maintenance and is not
damaging to the environment. As a thin surface over the cathodic
structure It erodes taking away the fouling organisms with it.
Hull Anodes on service vessels
Coatings are the first barriers to protect vessel hulls against corrosion. Due to microscopic
pinhole defects in the coating and damage to it whilst in service localised pitting will occur.
Hull/flush mounted anodes are used to complement the coating at areas of exposed steel
prolonging the life of the coating. Hull anodes are also employed to reduce corrosion rates
on areas of the hull that are local to propellers and the propellers themselves. Alloys of Zinc,
Aluminium and Magnesium with the necessary trace elements to provide correct
performance are used for the manufacturing of Sacrificial anodes
Even with correctly designed cathodic protection systems marine fouling is a constant
problem.
Anti-fouling paints and devices.
Mechanical:
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blasting devices e.g. sand abrasion,
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heated water in pipes and at power stations; different species have different tolerance,
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metal chains or foam skirting and other structures that move up and down girders, piling
structures, sometimes spinning
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ultra-sonic or low frequency resonators and vibrating structures to prevent settlement
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energizing a piezofilm layer carried on the outside of a vessel or structure to cause
mechanical vibration of the layer. This can be developed into a self- powered system. A
system including an electroded layer of piezoelectric material mounted in a position to be
stressed and strained and to then produce an alternating current (a.c.) voltage. This
piezoelectric material being coupled to voltage rectifying means for converting the a.c.
energy produced by the piezoelectric material when stressed and strained, into direct
current (d.c.) energy for charging a battery; and a direct current to alternating current
converter means coupled between the battery and the piezoelectric material for
converting the direct current energy stored in the battery into an alternating current
signal having a preselected frequency and applying the a.c. signal to the piezoelectric
material for causing the piezoelectric material to vibrate at a rate proportional to the
preselected frequency, to prevent settlement of fouling organisms.
Anti-fouling paints and devices.
Coating:
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anti fouling paints with toxic metals e.g. Tin, Copper or Lead; very toxic to all life in the
environment ; use banned.
these toxic metals micro-encapsulated for slower release; still toxic
Non toxic shiny slippery plastics and resins, some slowly breaking down and continuously
forming new surfaces; may slow down fouling but do not stop it.
superhydrophobicity (i.e. extreme non-wettability) research aimed at fabricating
superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e.
substratum texture) . The aim is the formation of responsive/‘‘smart’’ surfaces, which adjust
their physico-chemical properties to variations in some outside physical stimulus, including
light, temperature, electric field, or solvent. Finally, implications of tailoring the surface
chemistry, texture, and responsiveness of surfaces on the design of effective marine fouling
coatings are being considered.
Utilising Bioactive Compounds from marine invertebrates (e.g. sponges) algae, and
microorganisms, (produce to enhance their competitivity for space or to prevent other
organisms settling on their surfaces and overgrowing them).
Cyanobacteria produce a variety of bioactive metabolites that may have allelochemical
functions in the natural environment, such as in the prevention of fouling by colonising
organisms. Cyanobacterial metabolites have the potential for use in antifouling technology,
since they show antibacterial, antialgal, antifungal and antimacrofouling properties which
could be expoited in the prevention of biofouling on man-made substrata in the aquatic
environment. A survey of antibiotic compounds with antifouling potential revealed more than
21 different antifouling substances from 27 strains of cyanobacteria.
Anti-fouling paints and devices
Electrical:
• Galvanic or sacrificial anodes designed with a more negative
electrochemical potential than the metal of the structure (as described
previously), which gradually erode dislodging recently settled fouling
organisms.
• intermittent pulses of electric currents at various voltages along
submerged metal structures, often between short strips; some kill
organisms but some work by causing thin layers of the metal to slowly
fall off with time in a process similar to sacrificial anodes also dislodging
recently settled fouling organisms.
• an anti-fouling system that includes a pair of electrodes positioned apart
and a means for supplying an electrical current to the electrodes; The
electrolysis of sea water produces toxic agents such as chlorine and
sodium hypochlorite adjacent the aquatic body that removes barnacles,
algae, fungi and other marine growths. Further, the electrodes require
regular maintenance, which may be difficult.
Combating Marine Fouling
• Prevention of marine fouling
• Study Theory of processes involved in marine
fouling, to try and better understand how to
control it and limit its destructive powers and
in some cases utilise it for benefit.
Best Practice regarding Off Shore
Marine structures
• Spatial planning is important: to get the best sites
with the least damage to the environment, pre –
production (GIS studies)
• Environmental Impact Assessments (EIAs) are
necessary pre- and post-production
• Disposal or amelioration of structures / sites must
be considered early for the post-production phase.
Notes on Fouling
A.
Marine
Marine Fouling
1. Artificial substrates mimic natural ones when chosen properly
2. Non comparability between localities
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Workers vary substrate size, materials & observation techniques; select for
different animals; where possible keep features the same.
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Rarely can colonisation patterns on identical substrates from different latitudes be
compared.
3. Initial rates of increase in number of sessile species accumulating with time are
inversely related to latitude (in Northern Hemisphere: tropics to arctic); however
eventually have higher fouling in temperate versus tropical latitudes.
4. Initial dominance by colonial organisms changes to dominance by solitary
organisms in northern hemisphere, in contrast to tropical localities, where it is
the opposite (e.g. ending with colonial corals).
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Solitary: sexual reproduction more common.
Colonial: asexual reproduction more common.
Marine Fouling
5. Replicability
• Diversity is usually constant in an area
• Less variability among species totals than among species identities (species
substitution)
• Trophic dynamics the same: filter feeders are the most common
• 6 – 10 panels seem reasonable: benefits of larger sample size diminish quite
rapidly beyond this
• Although compositional differences exist between individual panels & may
well be the result of presence or absence of particular species, quantitative
descriptions of the colonisation process can accommodate these variations,
while still portraying many of the general aspects of colonisation.
Marine Fouling
6. Seasonal difference in colonisation
• Rate of colonisation increases in late spring; is low in winter:
• mussels may be an exception (highest in February / March).
7. In tropical localities colonial organisms eventually predominate
but it takes considerably longer (14 – 26 months) for them to
emerge as dominants over solitary species.
B. Protozoan Colonisation (Fresh Water):
(but probably the same in the marine environment for most species)
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There is an initial non interactive stage, followed by a longer interactive stage.
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Initial island colonisation is essentially a non-interactive process, primarily
influenced by the dispersal capacities and extinction potentials of the colonising
organisms.
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With the establishment of an equilibrium species number, interactive processes
such as competition and predation take precedence in determining the island’s
species composition.
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The island assemblage soon manifests the characteristics of an autonomous
community capable of maintaining its integrity in the face of environmental
change. (Ref. Zoology, Mac Arthur Wilson).
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Use plates as a sampling device:
a. may retrieve plates before equilibrium (where the numbers of individuals of species are
increasing) do not get very characteristic or repeatable results
b. or at equilibrium (where the numbers of individuals of species coming in are the same as
numbers leaving) get associated species assemblage.
c. Appropriate immersion time will vary under different environmental conditions, making
comparable sample days difficult to choose.
B. Protozoan Colonisation (Fresh Water):
2. Because the effectiveness of an artificial substrate sampler can be
affected differently by the factors of :
• Substrate size,
• Position in space, and
• immersion time,
• in a particular environment, it is preferable to:
a. hold size constant when comparing specific systems,
b. position substrates so they act as habitat islands, (need care in siting
them in characteristic regions),
c. monitor colonisation through time, as an alternative to one-time
sampling. A time–dependant process is then analysed as the indicator
of natural community structure.
3. Need sufficient size (5 X 7.5 X 6.5 cm) to collect the majority of species (of
Protozoa) from one location
• too large : is too time consuming & plate may become too heavy.
• too small : can sample poor competitors.
A.
Marine Fouling
8. Pioneer species (r-selection strategies): have high reproductive rates; live
in regions with unpredictable resources in unsaturated, non-equilibrium
communities; e.g. solitary ascidians (Cliona), more effort in reproduction.
9. Later species (K-selection strategies): lower reproductive rates, density
dependant mortality, specialised for habitat; e.g. solitary ascidians, e.g.
thicker tunic (Ascidia), less reproductive effort.
10. Interactive equilibrium succeeded by an "assortive" equilibrium: consists
of a combination of species that are either better adapted to the
conditions of the local environment, or else were able to coexist longer
with the particular set of species among whom they find themselves.
Simberloff expanded this concept of multiple equilibria to include
evolutionary and taxon cycle equilibria. He predicted that non-interactive
and interactive (including assortive) would be achieved on an ecological
time scale, and evolutionary and taxon cycle equilibria would occur on an
evolutionary time scale.
11. Substrate angle and predation as determinants in fouling Succession
Harris and Irons, working with sub-littoral populations in New Hampshire, tested
the hypothesis that ‘substrate angle and predation are determinants in fouling
community succession’ (vertical and lower horizontal surfaces would be expected
to have no crab predators, but may have starfish and fish predators).
The primary experiment involved arrays of 1/10-m2 plexiglass panels set up in
horizontal and vertical planes against and away from the wall of a wooden crib to
facilitate and inhibit access by sea stars, crabs and wrasses.
Two replicates of the experiments were established in summer and winter,
respectively, to test for temporal effects on long-term succession.
The results showed both substrate angle and predation effects, but no seasonal
effects.
• Siltation and predation interacted to exclude most species from the upper
horizontal surfaces, the exception being Mytilus edulis (mussels) in predator-free
systems.
• Lower horizontal surfaces had higher diversities and more species with upright
growth forms than vertical surfaces.
• Mussels dominated most surfaces on predator-free panels, regardless of substrate
angle.
• Predation effects included keystone predation (on mussels), larval filter (by
tunicates), and cropping of colonial species (hydroids and ectoprocts); in each
case, the survival and distribution of species had been altered.
• Inter-phyletic competitive interactions were documented and the results
suggested that size, longevity and a living surface layer are important mechanisms
enhancing the competitive abilities of encrusting colonial forms such as sponges.