Ocean Species Distribution
• Analyze factors that affect productivity and species distribution in marine and fresh water environments
Factors Affecting Ocean Species Productivity
• Several factors affect ocean species productivity
(reproductive success and life span). These
factors include:
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Ocean Temperature
Ocean Salinity (the ‘saltiness’ of the ocean)
Amount of oxygen in ocean
Acidity of ocean
• There have been significant changes in all of
these factors over the past few decades, which
has affected many ocean species around the
world.
Factors Affecting Ocean Species
Distribution and Productivity
• Some significant changes over the past few
decades have been:
1. The average ocean surface temperatures have
increased significantly since the 1970s
2. The ocean has become fresher (less ‘salty’ – lower
salinity) and more acidic in several areas worldwide
3. The amount of low-oxygen ocean areas have
increased
• We will now explore how these have affected
many species of animals
1. Increased Air and Ocean Water Temperatures
• The average ocean surface temperatures have increased
significantly since the 1970s
• The increase of these average ocean temperatures have had a
negative impact on the reproductive success of several
species of fish and sea mammals.
• For example, climate change directly affects the reproductive
success of sea turtles in three ways:
• 1. Sea level rise will affect significant nesting beach areas on low-level
sand beaches.
• 2. Rising temperatures increase the chance that sand temperature
will exceed the upper limit for egg incubation which is 34 degrees C.
• 3. Rising temperatures bias the sex ratio toward females because
temperature during incubation determines the sex of the egg. This
means that at a higher temperature, many more females than males
are born.
Ocean Species Distribution
• Temperature has shown to play the most important
role in ocean species distribution
• It has been shown that as ocean temperatures rise,
many ocean species are beginning to travel into the
cold and harsh Arctic waters.
• Other studies have shown that the distribution of
marine life shows two patterns:
– Coastal species (corals, coastal fishes, etc) tend to have
the highest diversity around Southeast Asia
– Open-ocean creatures (tunas, whales, etc) have much
higher diversity towards the middle of the oceans
2. Decreased Salinity & Increased Acidity of Ocean
• The ocean has become less salty (salinity has
decreased) around the world.
• This decreased salinity has lead to increased ocean
acidification (oceans being more acidic).
• This increased ocean acidification has greatly
affected several ocean species. The most significant
impact has been on marine organisms that build a
calcium carbonate skeleton or shell (i.e., scallops,
mussels, crabs, shrimp, starfish, etc), as the
increased amount of acid in the ocean does not
allow them to build these shells/skeletons as
effectively. This has decreased biodiversity.
3. Increased Low-Oxygen Areas in Ocean
• Low oxygen concentrations have been observed in a
number of ocean areas.
• Declines in oxygen concentration are caused by
changes in ocean circulation patterns, freshwater
inputs (i.e., more melting ice running into the ocean),
and rising temperatures.
• Low oxygen in the ocean has decreased the
biodiversity of species in Canadian waters by:
– Altering food webs (eliminating plants and animals)
– Favouring some species (those who can survive in lowoxygen zones) over others (those who cannot survive in
low-oxygen zones; i.e., bottomdwelling animals)
Marine Food Webs
• Ocean food webs have greatly changes over
the last few decades.
• One important change has been the changes
that have occurred in phytoplankton
(microscopic plants, bacteria, and algae, which
are the staple of food webs) blooms.
• Many phytoplankton blooms start earlier, are
more intense (greater), and last longer on the
Scotian Shelf than they used to.
Changes in Population Trends
• Many ocean species populations are interrelated.
• A significant trade has been found between the
populations of shrimp and groundfish (succh as
redfish, skate, atlantic cod, and snow crabs).
• It has been found that as the population of
groundfish decreases, the population of shrimp
increases.
• This is because groundfish feed on shrimp, and if
there are less groundfish, then shrimp
populations can bloom.