Environmental Factors Associated with Deep Chlorophyll Maxima in Dry Valley Lakes, South Victoria Land, Antarctica
Laura Burnett, Daryl Moorhead, Ian Hawes, Clive Howard-Williams
Environmental factors associated with deep chlorophyll maximum (DCM) layers were examined in five lakes of the McMurdo Dry Valleys, Antarctica, to test the hypothesis that DCM are more closely associated with resource limitations than water density. Because data could not be transformed to meet the assumption of normal distribution, distance matrices were constructed from vectors of observed chlorophyll-a (CHL), photosynthetic active radiation intensity (PAR), soluble reactive phosphorous (SRP), dissolved inorganic nitrogen (DIN), dissolved oxygen (DO), water density (DEN), and incremental change in water density/depth (DEL). Multiple regression analyses then were based on permutation evaluations of the relationships between distance matrices (partial Mantel analyses). Results indicated that resource availability (PAR and DIN) was most frequently related to chlorophyll-a, although DEN and DEL often were significant within individual lakes. Hence, resource relationships were strongest across lakes and seasons whereas density relationships also were important within individual lakes. Moreover, DCM appeared sensitive to threshold levels of DEN and PAR, suggesting that controls may exist as both discrete (threshold) and continuous functions of both resource availability and water density.