Life in the Open Ocean. Joseph J. Torres

of excitement over the last 50 years, with many expeditions to the fabulous communities inhabiting the hydrothermal vents at our planet’s oceanic ridges. More recently, the thrilling discovery of deep coral reefs off Australia has captured the public eye, showing that still more oceanic discoveries may yet await us.

      More fascinating yet are the communities of marine animals that inhabit the oceans’ pelagic realm, and the creatures’ adaptations to an environment devoid of barriers to movement in three‐dimensional space. Many people are familiar with the term “plankton,” the tiny plants and animals that drift with the ocean currents. More are familiar with the large pelagic species such as tuna, sharks, and swordfish, not only from pictures or fishing trips but also from the dinner table. The large, highly capable swimming species like tuna and sharks are termed “nekton.” In between the tiny drifters and the strong swimmers are an entire community of animals that are familiar mainly to oceanographers but are the critical link between the small and the large. Animals in the intermediate community are not as capable at swimming as the tunas but are better at it than the small zooplankton. Collectively, the creatures are known as the micronekton and macrozooplankton, and they make up one of the largest animal communities on planet earth.

      The nekton, micronekton, and macrozooplankton include a variety of different animal groups. Several different families of fishes are represented, many with unusual adaptations such as light organs like fireflies, huge gapes to allow them to swallow prey larger than themselves, and large tubular eyes. Among the invertebrates are shrimp similar to the ones we enjoy in shrimp cocktails and other crustaceans that can produce clouds of biological light or live inside jellyfishes. Among the jellies are species larger than a meter across and those that can double their population size in a matter of days by reproducing asexually.

The blue water pelagic community is truly fascinating. The problem is, to learn about the wonders we have briefly described above, you currently need to access many sources. Life in the Open Ocean: The Biology of Pelagic Species gathers the information available on the wide array of taxa making up the pelagic community and presents it as one cohesive whole. It is a synthesis of the information available on the biology of all the groups you will see if you tow a scientific trawl net between the surface and bathypelagic depths. When you bring the net up and look at your catch, you are looking at a community of coexisting species with each group having its own way of solving the problems posed by nature. The book combines basic information about the different animal groups as well as their different strategies for solving natures’ challenges.

      Topics covered in the book include basic physical oceanography, properties of water, physical variables that covary with depth such as light, temperature, and pressure and how animals have adapted to cope with each. Animal groups covered in depth (no pun intended) include the Cnidaria, or stinging jellies, the ctenophores or comb jellies, pelagic nemerteans, pelagic annelids, the Crustacea, the Mollusca including the “swimming snails” and cephalopods, the invertebrate chordates, including the salps, pyrosomes, and larvaceans, and lastly, the incredible fishes, focusing on the micronekton but also including the sharks, tunas, mackerels and mahi‐mahi.

      Within each of the animal phyla the pelagic groups are identified and detailed coverage is provided for classification and history, internal and external anatomy, vertical and geographic distributions, locomotion and buoyancy, foraging strategies, feeding and digestion, bioluminescent systems and their function, reproduction and development, respiration, excretion, nervous systems, heart and circulation and all sensory mechanisms: vision, mechanoreception (touch, balance, and vibration) and chemoreception (smell and taste).

      Life in the Open Ocean: The Biology of Pelagic Species is written so that it can be used as a textbook at the advanced undergraduate or graduate level of instruction, and as a reference for those interested in marine biology including professors, interested undergraduates, and perhaps for High School teachers teaching at the AP level. It is our fondest hope that it will make open‐ocean biology considerably more accessible, increasing its visibility and its presence in college‐level science curricula.

       Joseph J. Torres

       Thomas G. Bailey

      Acknowledgments

      Our heartfelt thanks to Dr. Dante Fenolio for the use of his fabulous images in Life in the Open Ocean: The Biology of Pelagic Species. They enabled us to show structures such as eyes, photophores, barbels and lures as well as whole animal appearance with freshly captured specimens, a boon for descriptions and a treat for the reader. As we progressed through the animal groups, specific questions arose that our longtime colleagues gave us help with. Advice on all things fish came from Dr. Tracey Sutton; questions on neurophysiology and bioluminescence were covered by Drs. Tamara Frank and Edie Widder; crustacean help came from Drs. Scott Burghart, Robin Ross, and Langdon Quetin; Claudia Mills gave us help with classification in cnidarians and ctenophores; and Eileen Hofmann and John Klinck helped with Antarctic physical oceanography. Special thanks to Bruce Robison and Alice Alldredge for the opportunity to dive WASP and Deep Rover many years ago. JJT would like to thank George Somero for a great sabbatical year and much biochemical advice over the years and Jim Childress for being the deep‐sea sage that he is. Many thanks to our friend Ms. Cynthia Brown who obtained many important publications for us as head of the interlibrary loan office at USF St. Petersburg.

      Study of open‐ocean biology requires going to sea in ships, and running a trawling or diving program at sea requires a team. As one progresses from being a participant in early days to principal investigator, field‐team leader, and chief scientist, the teams change, as do the ships, the nets, and if you’re really lucky, the submersibles. But, also if you’re lucky, you get to keep a few colleagues for several years. Foremost among those for JJT was his longtime research associate Joe Donnelly, colleague over two decades, and his co‐principal investigator Dr. Tom Hopkins, peerless zooplankton biologist and expert on the zooplankton fauna in three oceanic systems. For TGB his tireless research associate and good friend Gary Owen as well the crews of the ships and Johnson‐Sea‐Link submersibles at the Harbor Branch Oceanographic Institution provided invaluable support throughout his research career. All our colleagues mentioned above were with us on multiple cruises as well. JJT would like to thank my many graduate students, most of whom went to sea with me several times, some to the Antarctic, some to the Gulf of Mexico, some to the Caribbean, and some to Cariaco Basin. All are remembered here, and the reader will see their names many times in the text. In several cases, we were one science party in a multidisciplinary science team, examples of which were the AMERIEZ program discussed in the text, and the Southern Ocean GLOBEC program. Lastly, all the science teams were aboard research vessels, and the captains and crews of those vessels, and in the Antarctic our science liaison officers, made everything possible. Thanks to all.

      Lastly, the authors would like to thank the National Science Foundation and NOAA's National Undersea Research Program for funding our research over many years. Without their support, the research reported in here would have never happened, and not only ours but that of the multiple other labs whose research is cited in the book. Special recognition to Dr. G. Richard Harbison, exceptional gelatinous zooplankton biologist and never‐ending source of good humor who has crossed the rainbow bridge. We miss him.

1 Physics and the Physical Environment

      For many beginning the study of oceanic fauna, the ocean itself is a fairly mysterious place. We know that it is vast, deeper in some places than others, and that the deep sea is cold and dark. What is less clear is how physical factors vary over the global ocean and why they are the way they are. The purpose of this first chapter is to briefly describe the physical factors impacting pelagic (open ocean) animal life and how those factors are distributed in the world ocean in the horizontal and vertical planes. Physical factors play an important role in shaping the adapted characteristics of animal life, particularly physiological characteristics, and by virtue of being physical factors they vary predictably in space and time.

      One