Subsequent analyses showed additional relationships
between medusa abundance and climate. Purcell
& Decker (2005) used D.G. Cargo’s data from
1960–1995 (CBP, 2000) and found that medusa abundance
was negatively correlated with the NAOI from
the preceding December–March (Figure 4). Medusae
were extremely abundant in the 1960s when the
NAOI were generally negative. The 1960s were in a
cool, dry, regime, which shifted with Hurricane Agnes
in 1972 to a warm, wet regime that persists currently
(Austin, 2002). The regime shift was accompanied by
low medusa numbers and generally positive NAOI.
Shorter-term comparisons (1987–1990 and 1995–2000)
in mid-Chesapeake Bay showed that high April–May
salinities (P=0.006), warm July–August temperatures
(P=0.036), and high spring solar radiation (P