Sea Nettles Habitat

The habitat of a species is defined by multiple physical and biotic parameters. Though salinity and temperature were known to be important physical factors influencing the presence of sea nettles, a quantitative relationship between these variables has not been previously formulated for the entire Chesapeake Bay. We developed a bay-wide model to predict the probability of encountering sea nettles and their density in surface waters of the Chesapeake Bay by analyzing coincident data of nettle density, salinity and sea-surface temperature collected during the spring, summer and fall of 1987-2000 in surface waters of the bay and selected tributaries.

Concentrations of Chrysaora were found within a relatively narrow, well-defined range of temperature and salinity (26-30 °C and 10-16 PSU, Fig. 1).

The in-situ data were used to derive an empirical model that estimates the likelihood of sea nettle encounter, pnettles, as a function of salinity and temperature (Fig. 2):

pnettles = e^logit / [e^logit + 1],

where logit = -6.995 + (0.30 * temperature) - (0.469 *salinity_opt).

Temperature is in degrees celsius and salinity_opt is the difference between ambient salinity and optimal salinity for nettles (= 13.5 psu) as determined from in-situ observations.

A graphical representation of this model is presented below in Figure 2.