As the world warms and climate zones shift, species that are able may alter their range to try to keep themselves at a comfortable temperature. Although the oceans are generally warming more slowly than the land, migrations of marine species are well documented already. For organisms like fish, mobile adults can dynamically track suitable conditions. But many seafloor-dwelling critters primarily move in their wandering youth—as larvae that (mostly) passively ride the currents. Changing your destination isn’t so easy when you’re not in the driver’s seat.
Unfortunately, some of those species have been seen migrating the wrong way, toward even higher-temperature waters rather than away from them. We’ve seen this happen in the coastal northwest Atlantic, including in some commercially harvested species like clams. Seeing these species shift requires something unusual, since they’re adapted to their current-catching lifestyle. So what gives?
A team led by Heidi Fuchs at Rutgers University wanted to test the hypothesis that earlier spring warmth could explain things. These organisms take their spawning cue from warm temperatures, so long-term warming can push that springtime cue earlier and earlier. If the currents are different in early spring, that could lead to larvae drifting toward new locations simply because they’re ahead of schedule.