HAB Hotspots researchers have developed 3 hypotheses for Pseudo-nitzschia bloom and toxin initiation:

1. Blooms start as subsurface accumulations (subsurface maxima) and eventually manifest as surface blooms.

2. Blooms are predominantly caused by advective processes and retention in eddy-like circulation; subsurface maxima are less important.

3. There are a unique set of environmental conditions leading from bloom initiation to toxicity that can be identified through a comparative approach, allowing us to contrast potential factors (such as stratification, nutrient load, nutrient type) between regions.

The alternate hypotheses are that HAB events in California are truly stochastic and/or the underlying ecophysiological responses are so complex that relatively simple conceptual models such as proposed here do not adequately explain bloom and toxin initiation.