Question

northward spread of p. marinus
maine 1995
massachusetts 1994
long island sound 1992
southern new jersey 1982
upper chesapeake bay 1985 - 88
seaside of virginia and maryland 1985 - 88
lower chesapeake bay 1949
perkinsus marinus is a protozoan parasite that infects the eastern oyster and can be lethal. p. marinus was found in the lower chesapeake bay in 1949 and spread northward over the next several decades as shown in the figure. the parasite is transmitted from oyster to oyster and is most infectious at temperatures above 25°c and high salinities. which of these environmental changes is most likely to have contributed to the northward spread of p. marinus?
a. increased runoff into coastal wetlands
b. reduction in fish stocks
c. introduction of invasive plant species
d. increased ocean temperatures

Explanation:

To determine the environmental change contributing to the northward spread of \( P. marinus \), we analyze the parasite's requirements: it is most infectious at temperatures above \( 25^\circ \text{C} \) and high salinities.

• Option A: Increased runoff into coastal wetlands would likely decrease salinity (due to freshwater input), which is unfavorable for \( P. marinus \) (needs high salinity). Eliminate A.
• Option B: Reduction in fish stocks is unrelated to the parasite’s temperature/salinity requirements. Eliminate B.
• Option C: Introduction of invasive plant species does not directly affect temperature or salinity for the parasite. Eliminate C.
• Option D: Increased ocean temperatures can create conditions (temperatures above \( 25^\circ \text{C} \)) where \( P. marinus \) is more infectious, allowing it to spread northward as warmer temperatures become more common in higher latitudes.

Answer:

D. Increased ocean temperatures