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Speed of ocean temperature rises

Rising by 0.1 degree Celsius per decade (1960-2009)


Predictions of changes due to ocean temperature increase by 2100

Mora et al. 2013
Ocean surface temperature increased by 2-3 degrees Celsius
pH decline by 0.2 units
Oxygen concentration decrease by 2-4 units
Ocean productivity could decrease by 2% to 20%
Will affect all marine habitats
Effects greatest in surface waters and shallow habitats


When is the real change in marine habitats expected to come?

Marine habitats will enter new climate regime before terrestrial climate
Poorer countries will enter first


Potential impacts in marine life: organismal level

change in body size, reproduction, primary productivity, habitats


Potential impacts in marine life: population level

Changes in population growth, abundance, species distribution


Potential impacts in marine life: community/ecosystem level

Changes in community structure, trophic interaction, biodiversity


Potential impacts in marine life: fisheries/economics

Changes in fisheries catch, economics of fishing, fishery management


Potential impacts in marine life: global issues

Human population growth, migration, development, food supply and energy prices


Biogeographic shifts due to climate warming

Most species studied show poleward latitudinal shifts
However, some species show lower poleward distribution shifts than expected - they may be constrained by ‘essential’ habitat


Heatwave in south east Indian ocean

Wernberg et al. 2013
Caused massive shifts in abundance of local species


Evidence of results of marine heatwaves increasing in frequency

Smale et al. (2019)
More and more coral bleaching
Decrease in seagrass density
Giant kelp biomass changes


What causes “tropicalisation” of fisheries?

Poleward shifts and local abundance changes
Mean temperature of catch is increasing
(MTC = average inferred temperature preference of exploited species weighted by their annual catch)


Temperature and body size

Increased temperatures lead to greater metabolic costs
As environmental temperature increases from lower critical temperature, there is a linear increase in growth until pejus temperature is reached, after which growth rate declines rapidly and ceases at the upper critical temperatures
Smaller body sizes are therefore expected at high temperatures


What is phenology?

The study of the timing of life history events


Climate change and phenology

-Climate determines the timing of seasonal marine events
-Warmer temperatures may shift life history events to occur earlier
-E.g. NE Atlantic zooplankton blooms produced earlier in warmer waters


What is the match-mismatch hypothesis?

-Mismatch between prey and critical stages in their life history is known as the match-mismatch hypothesis
-Developed by David Crushing
-E.g Rhinoceros auklets in Japan - chicks grow faster and fledge successfully when fed on more anchovy, that in turn arrives earlier in warmer years