Phenology Effects
(^) Phenology is the study of the mechanisms that tune an organism’s life-history timing
to the cycling, generally seasonal cycling, of its ecosystem. The term is also used in
the form, “a butterfly’s phenology”, meaning its particular life-cycle adaptation to the
timing of habitat variation. One of the major features of climate change is shifting of
seasonal events, in particular winters end earlier with climate warming, springs start
earlier, so peak primary production comes earlier and growing seasons can last longer
if nutrients are continuously supplied. Peak seasons for 56 of 86 phytoplankton- and
zooplankton-species populations recurrently estimated by the CPR survey in the
northeast Atlantic have now shifted one to six weeks earlier than in the late 1950s and
early 1960s:
(^) “The general pattern observed for taxa that peak when the water column is mixed
or in a transitional state is to show considerable variability in phenology, whereas
taxa associated with low turbulent conditions have virtually all advanced in their
seasonality (34 out of 37 taxa between May–August).”
(^) (Edwards & Richardson 2004).
(^) That suggests that the date of stratification is a key seasonal event. Oddly, peaks of
a substantial fraction (26 of the 66 evaluated) shifted to later dates. Marine life will
not be wiped out by global warming (or acidification, either, see below), but
substantial shifts in the biota and rapid evolution of many populations are likely.
(^) Meanwhile, both plants and animals often use cues more fixed to the calendar,
particularly daylength variation, to time the onset and emergence from resting (or
diapause) stages, to meet for mating and spawning, to lay up lipid for diapause (all
key aspects of phenology). Diapause stages can also require a sufficient duration of
cold (or warm) conditions before emergence is enabled, such that significant
temperature change can prevent emergence. Thus, rapid shifts in the timing or
temperature of the periods of optimum or unsuitable habitat conditions will challenge
the evolutionary rates at which phenology can be shifted.
(^) On the other hand, life-history controls vary markedly within populations and thus
are subject to rapid selective modification. Probably there is a very long-term
population-level payoff for sustaining substantial phenological variability (that is, for
“bet hedging”). At least one planktonic copepod appears to be preadapted to respond
to shifting timing of the annual production peak. Neocalanus plumchrus in the
subarctic Pacific enters rest in late spring–early summer, then, within a few months,
begins to “meter out” maturation from its resting stage at depth. Males and females
mature sequentially over the time from about September to February, reproducing at
depth over that long period (Miller & Clemons 1988). The nauplii do not need to feed,