The spatial ecology of phytoplankton blooms in UK canals

Environmental change is expected to increase the frequency and severity of problems caused by harmful algal blooms. We investigated the ecology of phytoplankton blooms in UK canals to determine the environmental predictors and spatial structure of bloom communities. The results revealed a significant increase in bloom presence with increasing elevation. As predicted, higher temperatures were associated with a greater probability of blooms, but the relationship between temperature and bloom occurrence changed across landscapes. At the minimum level of agricultural land, the probability of bloom presence increased with increasing temperature. Conversely, at the maximum level, the probability decreased with increasing temperature. This pattern could be due to higher temperatures increasing phytoplankton growth rates despite lower nutrient concentrations at low levels of agricultural land, and nutrient depletion by rapidly growing blooms at high levels of agricultural land and temperatures. Community composition exhibited spatial autocorrelation; nearby blooms were more similar than distant blooms. Hydrological distances through the canal network showed a stronger association with community dissimilarity than Euclidean distances, suggesting a role for hydrological connectivity in driving bloom formation and composition. This new knowledge regarding canal phytoplankton bloom origin and ecology could help inform measures to inhibit bloom formation.