Climate Change and Range Shifts. Hopkins Marine Station, site of Barry et al. 1995. Example 1: Barry et al. 1995. Hopkins Marine Station is located in Monterey Bay
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Hopkins Marine Station, site of Barry et al. 1995
solid = P<0.05Barry et al. 1995: changes in species composition
Trends are consistent with hypotheses that:
- southern spp. are expanding
- northern spp. receding to higher latitude
similar latitudinal rage shifts have been observed for terrestrial species
Sea surface temperature records indicate a major shift in temperature regimes occurring in 1975-1976.
Such shifts are part of a normal multi-decadal cycle in the north Pacific ocean, but global climate change appears to be affecting the cycles, making the upward part of the cycles greater than the downward, so that long term temperatures are ratcheting up.
Sea surface temperature records
indicate major regime shift in
part of a normal multi-decadal
cycle in north Pacific
Global climate change may make
warm cycles warmer
long term temperatures are
Negative correlation between °C and (a) fish diversity, or
(b) abundance of northern species, does not indicate any
mechanism or causation for change
Higher sea surface temperature could have:
- direct effects on fish physiology, lowering either survival
or reproduction of northern spp.
cold surface water often causes high fertility
- indirect effects – e.g., diminishing food supplies
high surfaces temps can restrict nutrient availability,
ocean productivity, and hence food availability
... or the correlation could be coincidence; more work needed
Harley presents evidence to support of the idea that the extinction of mussel beds in some areas of the Salish Sea (Puget Sound) results from temperature stress with climate change.
Wave exposed: broad zones
Sheltered: compressed zones
Along a west-east transect, he compared temperature and zonation as it exists today (grey squares) and a change in mussel and barnacle zonation from 1957 to 2010 (gray circles). Lower graph shows low tide temperatures measured at sites indicated by squares.
Along east-west transects, compared:
°C& zonation today
change in mussel + barnacle zonation
from 1957 to 2010 (gray circles)
low tide temperatures
measured at sites
The upper limits of barnacles and mussels measured on 2009 sites (squares in previous slide) are negatively correlated with temperature (plots A-D). Sea star heights measured at low tide show no statistically significant relationship with low tide temperatures (plot E).
- air temperatures in Victoria (city
midway along transect) increased
- upper limits of barnacles & mussels
moved down shore
- lower limits showed no significant change
- some mussel beds in wave-sheltered
eastern end of transect went extinct
conclusion: increasing temp. stress
caused upper limit of refuge to drop,
vertically compressing mussel zones
- naturally compressed mussel zones
in the east just disappeared
Sea star “Browse Lines”
Sea stars sometimes forage above
the lower boundary of mussel beds removing small, preferred prey, including barnacles and small mussels.
Their foraging appears to be more flexible than assumed by the refuge hypothesis.
D. R. Blakeway and C. D. Robles, Department of Biological Sciences, California State University at Los Angeles, CA 90032.
Study site Southern California.
on Bird Rock
Bird Rock east end, winter 1984 Southern California.
Bird Rock east end, March 1987 Southern California.
Bird Rock east end, April 1991 Southern California.
Bird Rock east end, March 1993 Southern California.
Bird Rock east end, October 1999 Southern California.
Using a camera on a pole one can take overhead views, which are easier to analyze
Bird Rock east end photo-mosaic, March 2001
Image analysis software can be used to covert panoramas to an overhead view
Mussel abundance Bird Rock East, 1983-2000 an overhead view
What happened in 1983-86 and 1991-93?
SST Catalina Ridge/Two Harbors, 1982-2001 an overhead view
Major el nino (warm water) events in blue
Zooplankton abundance, SoCal Bight, 1950-2000 an overhead view
Could the recent (since the late 1970s) decline in zooplankton abundance be the result of declining ocean production? If so, what are the implications for mussels?
Severe El nino years in orange.
Assuming that mussel zones are indeed collapsing in the Salish Sea, can you formulate an alternative hypothesis to Harley 2011?