How to optimize microalgae ratios for stage specific feeding in copepods and bivalves.

Microalgae, being varied organisms have different cell sizes and morphological characteristics that distinguish them from each other, playing a crucial role in determining how to feed your filter feeders.

Let's start at the D hinge stage of bivalve larvae. Here, you see that Isochrysis/Tisochrysis is required in conjunction with a diatom like Chaetoceros muelleri. This is because early larval development in both bivalves and copepods require DHA, a fatty acid required for growth. However, as the larvae start to reach 120 microns in mean shell length, around the Velinger stage of development, they require a third microalgae called Tetraselmis to fuel metamorphosis. Tetraselmis is preferred over other microalgae species for it's high carbohydrate content, which is important for later stages.

The main limitation here is using bioavailable microalgae in the right size based on the current stage. Bivalve larvae are strictly limited to feeding from their esophagus, whereas copepods are less constricting. Notice how nannochloropsis is not added-the cells walls are extremely unsuitable for bivalve larvae, and only pose value for copepods.

So why not just use one algae strain? The truth is simple- one microalgae cannot cover all the nutrients bivalves need. "Mixed algal diets are beneficial. A combination of two or three high nutritional value species including a suitably sized diatom and a flagellate invariably provide improved rates of larval growth and development than do single species diets (Figure 68). They also improve spat yields and influence the subsequent performance of spat in terms of both growth and survival." (Figure 68) This means if you want your creatures to be the most healthy they can be, using mixed diets such as ours is the best way to go.

The hatchery culture of bivalves: a practical manual

Nutritional properties of microalgae for mariculture - ScienceDirect