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Lord J.P.,University of Connecticut | Shanks A.L.,Oregon Institute of Marine Biology
Marine Biology | Year: 2012

Body size has great influence on feeding, reproduction, and ecological importance. This study measures growth, reproduction, and feeding for several northeastern Pacific intertidal invertebrates that have indeterminate growth. In all species studied, linear size (length, diameter) showed asymptotic growth fit by the von Bertalanffy growth function, supporting the notion that less energy is allocated to growth with age because of increased reproduction. However, these same species displayed a continuous, roughly linear increase in volume with age. Both reproductive output and food intake were shown to scale proportionally with volume. This indicates that some species with indeterminate growth do not reduce energy allocation to growth with age but instead display continuous volumetric growth that facilitates increases in feeding rate and reproductive output with age and size. A simple allometric model is proposed to describe constant volumetric growth rates and linear increases in reproduction with age. © 2012 Springer-Verlag.

News Article | November 28, 2016
Site: www.eurekalert.org

PULLMAN, Wash. - As long as ecologists have studied temperate lakes, the winter has been their off-season. It's difficult, even dangerous, to look under the ice, and they figured plants, animals and algae weren't doing much in the dark and cold anyway. But an international team of 62 scientists looking at more than 100 lakes has concluded that life under the ice is vibrant, complex and surprisingly active. Their findings stand to complicate the understanding of freshwater systems just as climate change is warming lakes around the planet. "As ice seasons are getting shorter around the world, we are losing ice without a deep understanding of what we are losing," said Stephanie Hampton, a Washington State University professor and lead author of a study published in the journal Ecology Letters. "Food for fish, the chemical processes that affect their oxygen and greenhouse gas emissions will shift as ice recedes." "A lake doesn't go to sleep when it's covered with a blanket of ice and snow," said Liz Blood, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "While winter's lower temperatures and light levels may force lake life into a slower mode, algae and zooplankton are still abundant. "What will happen if lake ice cover decreases in warming temperatures?" she said. "These results are a significant step in understanding what may be far-reaching changes for lake ecosystems." Fresh water is fundamental to society. We use it for drinking, manufacturing, energy production, irrigation and fish - a particularly important protein source in the developing world. Global warming is expected to change what we value in fresh water, as a study co-authored by Hampton last year found lakes warming around the world. The new study finds that what happens in the winter can have a substantial effect on what happens during the rest of the year. This is especially true for lakes that let in a lot of sunlight, stimulating the growth of algae and zooplankton on the underside of the ice. These in turn serve as food sources for fish at the start of their growing season. "In some lakes where the ice is really clear and there's not very much snow cover, there can be a lot of photosynthesis and a lot of productivity," said Hampton, who has extensive experience studying Lake Baikal in Russia, the world's deepest lake. "So there were some lakes in this study where the productivity in winter actually exceeded the productivity you would see in summer." Hampton said her Russian colleagues have seen "a unique little microecosystem" under the ice, with filaments hanging down from the subsurface. "It's interesting to think about these lakes that get a lot of light through the ice," she said. "Russian researchers who spend a lot of time on Baikal remind us that when you get ice, now you've got a new habitat. It can be a vast habitat extending across the entire lake." Marine biologists have documented a key role of sea ice in supporting polar food webs. "Under sea ice, you see the growth of foods higher in beneficial fatty acids and contributions as high as 30 percent to overall annual productivity," said Oregon Institute of Marine Biology's Aaron Galloway, a coauthor who was a postdoctoral fellow at WSU when the study began. But until this study, freshwater scientists "were not able to make any sort of estimates like that at all," said Hampton. Investigations of frozen freshwater bodies were just too spotty. Indeed, the International Society of Limnology's Plankton Ecology Group, which has been highly influential in aquatic science, has developed a theoretical model of lakes incorporating the interplay of plankton, nutrients, temperatures and mixing. But in 2011 the group said, in effect, that winter was being overlooked.v "It was a pretty strong statement about how little we know about winter," said Hampton. So she and her fellow lake ecologists posted a request for data on a listserv of professional colleagues, expecting maybe 30 responses. They got 140 responses from researchers with measurements of various winter conditions, like plankton and nutrient levels, that could be compared to summer values. Their findings varied a lot, often depending on whether a lake was covered with clear ice or covered with snow that blocked most light. "In some cases, we know that zooplankton under ice are really important for seeding the populations that will take off in the summer and grow to be more abundant," said Hampton. In other cases, there may be algae consuming large amounts of nutrients under the ice so the summer algae have less for their own growth. Climate change stands to introduce another set of considerations. "A number of things are changing, with climate change, that actually affect the characteristics of the ice itself," Hampton said. The ice season can be shorter. There can be less snow, which will let in more light. Or there can be more rain during ice formation, making the ice cloudy. Predicting these changes, she said, "will not be straightforward." Regardless, lake scientists will need to break out their winter gear. "Overall, this study tells us that limnologists no longer have any off-season," Hampton said. "No more down time, especially as we're losing ice so rapidly."

Meyer K.S.,Oregon Institute of Marine Biology | Bergmann M.,Alfred Wegener Institute for Polar and Marine Research | Soltwedel T.,Alfred Wegener Institute for Polar and Marine Research
Biogeosciences | Year: 2013

Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007, and 2012 at the shallowest station (HG I, ∼1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The community of HG I may be unique in its response to elevated food input, which resulted in higher evenness and diversity in 2012. © 2013 Author(s).

Brooke S.,Oregon Institute of Marine Biology | Ross S.W.,University of North Carolina at Wilmington | Bane J.M.,University of North Carolina at Chapel Hill | Seim H.E.,University of North Carolina at Chapel Hill | Young C.M.,Oregon Institute of Marine Biology
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013

Water temperature may be a primary exogenous determinant of deep-sea coral distributions. The upper thermal threshold for survival of the deep-water coral Lophelia pertusa (Linnaeus, 1758) is generally accepted to be ~12-14. °C, based on field observations of coral distributions. However, hydrographic conditions over coral mounds are dynamic on various scales, often producing temperature fluctuations of unpredictable duration and magnitude. This study investigated the survival of L. pertusa under a range of experimental temperatures: 5, 8. °C (ambient), 15, 20 and 25. °C, for two experimental durations: 24. h and seven days. There was a significant difference (p<0.001) in survival among temperatures after both the 24. h and the seven day experiments. The experimental data were supported by survival data for coral fragments deployed on benthic landers off North Carolina, where historical data show that temperatures over coral mounds vary greatly and reached 15. °C on a recurring basis. Experimental and in situ data suggested that the upper lethal temperature limit for this deep-sea coral species is near 15. °C. Tolerance to fluctuations in environmental variables, such as temperature, decreases the probability of mortality in the face of anomalous events and/or variable environments. Understanding the eco-physiology of structure forming deep-coral taxa will help inform management strategies; for example, preserving those ecosystems that are more resilient to threats from predicted changes. © 2012 Elsevier Ltd.

Vendetti J.E.,California State University, Los Angeles | Trowbridge C.D.,Oregon Institute of Marine Biology | Krug P.J.,California State University, Los Angeles
Integrative and Comparative Biology | Year: 2012

Credible cases of poecilogony, the production of two distinct larval morphs within a species, are extremely rare in marine invertebrates, yet peculiarly common in a clade of herbivorous sea slugs, the Sacoglossa. Only five animal species have been reported to express dimorphic egg sizes that result in planktotrophic and lecithotrophic larvae: the spionid polychaete Streblospio benedicti and four sacoglossans distributed in temperate estuaries or the Caribbean. Here, we present developmental and genetic evidence for a fifth case of poecilogony via egg-size dimorphism in the Sacoglossa and the first example from the tropical Indo-Pacific. The sea slug Elysia pusilla produced both planktotrophic and lecithotrophic larvae in Guam and Japan. Levels of genetic divergence within populations were markedly low and rule out cryptic species. However, divergence among populations was exceptionally high (10-12 at the mitochondrial cytochrome c oxidase I locus), illustrating that extensive phylogeographic structure can persist in spite of the dispersal potential of planktotrophic larvae. We review reproductive, developmental, and ecological data for the five known cases of poecilogony in the Sacoglossa, including new data for Costasiella ocellifera from the Caribbean. We hypothesize that sacoglossans achieve lecithotrophy at smaller egg sizes than do related clades of marine heterobranchs, which may facilitate developmental plasticity that is otherwise vanishingly rare among animals. Insight into the environmental drivers and evolutionary results of shifts in larval type will continue to be gleaned from population-level studies of poecilogonous taxa like E. pusilla, and should inform life-history theory about the causes and consequences of alternative development modes in marine animals. © The Author 2012. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved.

Bird A.M.,Oregon Institute of Marine Biology | von Dassow G.,Oregon Institute of Marine Biology | Maslakova S.A.,Oregon Institute of Marine Biology
EvoDevo | Year: 2014

Background: For animal cells, ciliation and mitosis appear to be mutually exclusive. While uniciliated cells can resorb their cilium to undergo mitosis, multiciliated cells apparently can never divide again. Nevertheless, many multiciliated epithelia in animals must grow or undergo renewal. The larval epidermis in a number of marine invertebrate larvae, such as those of annelids, mollusks and nemerteans, consists wholly or in part of multiciliated epithelial cells, generally organized into a swimming and feeding apparatus. Many of these larvae must grow substantially to reach metamorphosis. Do individual epithelial cells simply expand to accommodate an increase in body size, or are there dividing cells amongst them? If some cells divide, where are they located?Results: We show that the nemertean pilidium larva, which is almost entirely composed of multiciliated cells, retains pockets of proliferative cells in certain regions of the body. Most of these are found near the larval ciliated band in the recesses between the larval lobes and lappets, which we refer to as axils. Cells in the axils contribute both to the growing larval body and to the imaginal discs that form the juvenile worm inside the pilidium.Conclusions: Our findings not only explain how the almost-entirely multiciliated pilidium can grow, but also demonstrate direct coupling of larval and juvenile growth in a maximally-indirect life history. © 2014 Bird et al.; licensee BioMed Central Ltd.

The gumboot chiton Cryptochiton stelleri Middendorff, 1847, is the largest intertidal invertebrate herbivore in the northeast Pacific, but little is known about the fine-scale distribution of this species within its range. In this study, extensive intertidal surveys were used to determine the distribution of C. stelleri within six rocky intertidal sites on the southern coast of Oregon, USA, and found that gumboot chitons show a patchy and clumped distribution. At all six sites, individuals were found at highest densities within small coves, and small specimens (< 15 cm long) were found almost exclusively in sea urchin pits. Age-frequency histograms were created for populations of C. stelleri at all six sites and showed sporadic cohort success, likely as a result of sporadic recruitment. Successful cohorts were indicated by peaks in the age-frequency histograms and were compared between sites in order to determine whether or not successful cohorts occurred at the same time at all sites. There was low similarity between sites, and a negative correlation was found between distance between sites and percent similarity in age-frequency peaks. Combined with other factors, this suggests that larval settlement and cohort success of C. stelleri is driven by local factors, not such large-scale factors as upwelling or El Nio.

Cryptochiton stelleri is the largest herbivore in the intertidal and subtidal zone throughout its North Pacific range, but its larval development and metamorphosis have not been well documented. A description of larval development for specimens in Hokkaido, Japan, has been used in multiple textbooks yet shows many features atypical of chiton development. In the present study in Oregon, C. stelleri larvae were raised in culture and displayed developmental stages similar to other chitons, very different from the previous description. Plate development began 3 days after hatching. Larvae were competent beginning 3 days posthatching and metamorphosed in response to extract from encrusting coralline algae. Larvae survived for over a month without metamorphosing and did not metamorphose in response to increased temperature, presence of adults or the addition of algal foods of adults or juveniles. Juvenile C. stelleri were discovered in the field and grew c. 4 mm per month in captivity. Juveniles had exposed shell plates and fed on the red alga Cryptopleura. © The Author 2011.

Brooke S.,Oregon Institute of Marine Biology | Jarnegren J.,Norwegian Institute for Nature Research
Marine Biology | Year: 2013

Between 2002 and 2008, samples of the cold-water scleractinian coral Lophelia pertusa were collected from the Trondheim Fjord in Norway to examine reproductive periodicity. Collections were made from three locations: Tautra, (63°35. 36′N, 10°31. 23′E at 40-70 m), Stokkbergneset (63°28. 18′N, 09°54. 73′E at 110-500 m), and Røberg (63°28. 88′N, 09°59. 50′E at 250 m). Populations of L. pertusa from the Trondheim Fjord initiated oogenesis in January and spawning occurred from late January to early March the following year. Gametogenic cycles of the female L. pertusa samples overlapped by approximately 2 months, with oogonia visible in January, but this was not evident in the males. This paper provides the most complete gametogenic cycle to date and spawning observations for this important structure-forming species. The results from fjord populations are compared with published and preliminary data from other regions and are discussed in the context of regional differences in physical and biological variables, particularly food supply. Differences in gametogenic cycles within a single species provide a rare opportunity (especially in deep-sea species) to examine potential drivers of reproduction. © 2012 Springer-Verlag.

Von Dassow G.,Oregon Institute of Marine Biology
Methods in Molecular Biology | Year: 2014

It is almost impossible to use a confocal microscope without encountering the need to transform the raw data through image processing. Adherence to a set of straightforward guidelines will help ensure that image manipulations are both credible and repeatable. Meanwhile, attention to optimal data collection parameters will greatly simplify image processing, not only for convenience but for quality and credibility as well. Here I describe how to conduct routine confocal image processing tasks, including creating 3D animations or stereo images, false coloring or merging channels, background suppression, and compressing movie files for display. © 2014 Springer Science+Business Media, New York.

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