Bottom Trawling Flashcards
Ocean biodiversity
Large structure former live in shallow water and small structure fprmers live in deep water ( esp the Abyssal Muddy plains)
Creatures in large structure formers
Kelp forest - support diversity
Mangrooce - stabilize sediment, prevent over siltation
Coral reef - prevent erosion
Sea bed - prevent over siltation
Creatures in small structure formers
Epifauna above the seafloor of sediments
Infauna- within the seafloor sediment where o2 penetrates
Importance of benthic species
Nutrient cycling
Pollutamt distribution and fate - resuspension transport & metabolize
Secondary production - habitat, food, water
Water clarity- buffer nutrient loading
Sediment stability and transport
Bottom trawls
Net dragged over the seafloor to catch fish
Bottom trawling damages
Penetrate and scrape the seafloor , affecting marine lofe and structures
Impacts of bottom trawling
Re-suspension of mud , infauna and pollutants
Loss of fauna
Loss of microstructure
Sediment trail
Cold-water/deeo coral reef affected by disturbances
Vulnerable matine ecosystem
Impacts a high biodiversity
Magnitude of the issue
Most seafood from bottom trawling
Global continent shelf area trawled every year
- high sea impacts are unregulated
Fishing effort not randomly dostributed
Causes seascape fragmentation
Long term impacts on benthic communities
1- species area relationship
2- Succession- change in community structure through time
Influence of sps richness btw disturbance ecvents
3- island biogeography theory
Size pf untrawlled habitat fragments & distance btw fragments influences sps richness
Long term impacts on benthic communities
1- species area relationship
2- Succession- change in community structure through time
Influence of sps richness btw disturbance ecvents
3- island biogeography theory
Size pf untrawlled habitat fragments & distance btw fragments influences sps richness
Disturbances
Event that affects ecosystem structure and function
Dusturbance regime
= patterns if disturbance events
- intensity - idv or sps /event
- scale - spacial extent
- frequency - mean number (linked to int or scale)
Scale : frequnecy : intensity
Small scale- high frequency, low intensity
Large scale- low freq, high int
Succession
- change in comm structure through time
- colonization & extirpation rate
Colonization vs extirpation
Colonization - high sps richness
Extirpation - dec sps richness
Early colonizer / pioneer vs later colonizer / climax
R-selected- Early colonizer have high r , poor comp
K - selected- Later colonizer low r , better comp
Disturbance frequency
High frequency -> early sps only - reduce sps richness
Island biogeography theory- speciecs richness depends on
Colonization rate and extirpation rate
Island biogeography theory - two prediction
- distance btw untrawled areas inc -> colonization rate dec = sps richness dec
- size btw untrawled areas dec ->extirpation rate inc = sps richness dec
Practical solutions of bottom trawling
Full ban on bottom trawling & dredging in intn waters or high sea - 45% of searths surface
Stop trawling in sensitive areas like VULNERABLE MATINE ECOSYSTEM
Bottom trawling effects on natural disturbance regime
Low natural disturbances in shaloow water
High in deeper water - adap to low disturbances
Bottom trawling effect on trawling disturbance regime
Leads to large scale , high frequency and high intensity disturbances
Keading to only early species thrive - red sps richness
Bottom trawling effect over time
Target sps catch DEC
recovery rate of pop DEC
HIGH bycatch -> LOW bycatch
Biodiversity of infauna DEC - less o2 penetration less diversity
Complexity in benthic structures DEC
rare scavabger sps INC feed on sus benthic sps
Bottom trawling vs clearcutting
• Similarities:
o Alter substratum
o Remove structure-formers ]
o Maintain early and eliminate late successional stages (decrease biodiversity)
o Remove high biomass from ecosystem
• Differences:
o Larger area of seafloor impacted
