ABSTRACT
The factors to which blooms are commonly attributed are increased availability of combined nitrogen (nitrate or ammonia) or phosphorus, or changes in the hydrography of the location (Table 1). Nitrogen has been identified as the most limiting nutrient in many of the studies shown in Table 1, but not always unequivocally, because phosphorus is also implicated in many blooms. The case for the involvement of increased nitrogen availability in bloom development has sometimes been made on the basis of focused experimentation, but there is often an assumption that nitrogen is involved because of the known low availability of nitrogen relative to other resources needed for macroalgal growth in coastal waters. Increases in phosphorus alone may cause some blooms, and changes in hydrography, induced by road construction or nearshore geological events, can also promote bloom conditions (Table 1). It seems likely that many blooms are caused by various combinations of changes in all three of these factors (nitrogen, phosphorus and hydrography) and perhaps others (Lowthian et al. 1985).
