Transport
When eastern oysters spawn eggs and sperm into the water, fertilization creates billions of larvae that swim and feed on microalgae for 2-3 weeks before settling, cementing themselves on the bottom, and metamorphosing (changing form) into a tiny juvenile oyster (life history link). Larval swimming abilities are very weak, so tidal and river currents potentially carry the larvae to new locations, some good and some bad for survival. We want to know if oyster larvae settle more in some locations than others, so that habitat restoration can target locations with a greater potential for natural seeding and a sustainable supply of offspring. Physically sampling the tiny swimming organisms (zooplankton) and trying to find dispersed oyster larvae to learn where they go would be like grasping at dust, when it is glittering in a sun beam, and trying to determine which particles came from the couch pillow. Instead, we model larval dispersal by reconstructing (in a computer) all the water movements and “release” computer-code larvae that largely move with the currents, but also are programmed to behave as we think larvae behave. Within the estuarine domain of the model, then, we can track dispersing larvae and measure if the water currents carry them out of the model domain (e.g. into the ocean where survival is unlikely), or where they “settle” within the model domain. This is done by simply recording where each computer larva is located XX days after release.
As you might imagine, different release locations yield different settlement patterns. In the Hudson River Estuary there is only one known native breeding population. The location of this remnant population, north of Manhattan near the Mario Cuomo bridge, therefore provides an important set of release locations for which the model will predict where oyster settlement is likely to be most abundant. Other release locations are of interest because model results can suggest which locations, if adult oysters were successfully restored there, would contribute most to larval settlement in areas known to have suitable hard settlement substrate.
The model domain map below allows you to select a region for further investigation on how larvae are transported by tidal currents. Click on a highlighted sub-region to view simulations for transport in the highlighted area.