The ocean’s midwater zone is dominated by gelatinous predators such as ctenophores, siphonophores, and hydromedusae. These mysterious creatures still hold many secrets like how and why they make light, and how they survive in such an extreme environment. Which of these diverse groups help indicate the state of the ecosystem and potentially signal change? MBARI is one of very few institutions that has had an ongoing dedication to understanding this habitat and addressing these difficult-to-study organisms.

Steve Haddock’s lab aims to characterize and monitor gelatinous plankton through several approaches. A primary goal is to determine the identity and relationships of animals, so that they can be accurately recognized from images or DNA samples. With this knowledge, we can better make use of existing MBARI data to “go back in time” and see what changes have already been occurring. Using emerging methods to identify cryptic genetic diversity, we can determine the true community composition of the midwater habitat. This is important because it is not possible to “count up” organisms until we are able to recognize them accurately. We will also continue the development of broadly applicable tools that make use of MBARI’s unique video archives to study long-term trends.

By sequencing genomes (all the DNA) and transcriptomes (DNA that is being turned into proteins at a given time), we can gather novel insights about how organisms make light, how they are related, and how they adapt and survive in the challenging deep-sea environment.

Know Your Ocean


Bioluminescence—nature’s living light—is common among deep-sea animals. MBARI research is revealing how and why animals produce their stunning light shows.



Hetherington, E.D., C.A. Choy,  E.V. Thuesen, and S.H.D. Haddock. 2022. Three distinct views of deep pelagic community composition based on complementary sampling approaches. Frontiers in Marine Science, 9(864004): 1–10.

Johnson, S.B.,  J.R. Winnikoff,  D.T. Schultz,  L.M. Christianson,  W.L. Patry, C.E. Mills, and S.H.D. Haddock. 2022. Speciation of pelagic zooplankton: Invisible boundaries can drive isolation of oceanic ctenophores. Frontiers in Genetics, 13(970314): 1–17.

Schultz, D.T., W.R. Francis, J.D. McBroome, L.M. Christianson, S.H.D. Haddock, and R.E. Green. 2021. A chromosome-scale genome assembly and karyotype of the ctenophore Hormiphora californensis. G3 Genes|Genomes|Genetics, 11(11): 1–12.

Hsin, Y.L. and S.H.D. Haddock. 1997. The enclosing latticed sphere of Tuscaridium cygneum (Murray), a eurybathyal phaeodarian Radiolaria, from the North Pacific. Paleontological Research, 1: 144–149.


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