Were those BG in the pic?

As a water quality indicator ... what attributes of water quality do Bryozoa indicate? The few photographs I have seen show them associated with very green water with low visibility. The same applies to the OP's photograph. I usually associate high water quality with very clear water so I figure I am missing something with regard to what qualifies water as high quality. Would an organism like this be more abundant in clear waters or are they more likely to occur with high concentrations of living organisms in the water column like are present in the OP's photograph? It occurs to me they may be sensitive to toxins, pesticides, and herbicides and that this is the water parameter being referred to. Organisms in water cycle quickly but a colonial organism like a bryozoan is long lived so a photograph doesn't necessarily depict the environment they thrived or grew in.