Global mesozooplankton communities show lower connectivity in deep oceanic layers

Area of Science:

• Marine Ecology
• Oceanography
• Molecular Ecology

Background:

• Mesozooplankton are crucial for ocean carbon cycling and energy transfer.
• Global knowledge of mesozooplankton diversity, distribution, and connectivity is fragmented.
• Understanding these communities is vital for predicting ocean ecosystem responses.

Purpose of the Study:

• To assess global mesozooplankton diversity and distribution using DNA metabarcoding.
• To identify oceanic regions with significant undiscovered biodiversity.
• To investigate factors structuring mesozooplankton communities across depths and basins.

Main Methods:

• DNA metabarcoding of mesozooplankton samples from the Malaspina-2010 circumnavigation.
• Analysis across Atlantic, Indian, and Pacific oceans from surface to bathypelagic zones.
• Examination of alpha- and beta-diversity patterns and community structuring.

Main Results:

• Significant gaps in knowledge of global mesozooplankton diversity were confirmed.
• The Indian Ocean and deep sea harbor the highest proportion of hidden diversity.
• Mesozooplankton communities show horizontal and vertical structuring, with increased beta-diversity and reduced connectivity with depth.
• Bathypelagic communities are structured by water mass types, unlike upper layers structured by oceanic basins.
• Limited dispersal in deep ocean layers is suggested, influenced by currents and water mass mixing.

Conclusions:

• Global mesozooplankton diversity is underestimated, with critical hotspots in the Indian Ocean and deep sea.
• Depth and water mass type are key drivers of mesozooplankton community structure in the deep ocean.
• Oceanic currents and barriers play a significant role in shaping global plankton connectivity, particularly in deeper waters.