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Angel, MV, Checkley Jr. DM, Heany SI.  1985.  Chapter One: Plankton migrations. Introduction. Contributions in marine science volume 27 supplement. ( Rankin M, Wohlschlag DE, Eds.).:43-44., Port Aransas, TX: Port Aransas Marine Laboratory, University of Texas Marine Science Institute Abstract
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Asch, RG, Checkley Jr DM.  2013.  Dynamic height: A key variable for identifying the spawning habitat of small pelagic fishes. Deep Sea Research Part I: Oceanographic Research Papers. 71:79-91.   10.1016/j.dsr.2012.08.006   AbstractWebsite

Small pelagic fishes off southern California exhibit interannual variations in the regions they occupy. An enhanced understanding of these fluctuations could improve fisheries management and predictions of fish's responses to climate change. We investigated dynamic height as a variable for identifying the spawning habitat of northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), and jack mackerel (Trachurus symmetricus). During cruises between 1998 and 2004, dynamic height was calculated from temperature and salinity profiles, while fish egg concentration was measured with obliquely towed bongo nets and the Continuous, Underway Fish Egg Sampler. Dynamic height ranged between 68 and 108 cm, with values increasing offshore. The greatest probability of encountering anchovy, sardine, and jack mackerel eggs occurred at dynamic heights of 79–83 cm, 84–89 cm, and 89–99 cm, respectively. Four mechanisms were proposed to explain how dynamic height affects egg distribution: (1) dynamic height is a proxy for upper water column temperature and salinity, which are known to influence spawning habitat. (2) Low dynamic heights are indicative of coastal upwelling, which increases primary and secondary productivity. (3) Egg concentration is greater at dynamic heights coincident with geostrophic currents that transport larvae to favorable habitats. (4) Eddies delineated by dynamic height contours retain eggs in productive habitats. To evaluate these mechanisms, a generalized linear model was constructed using dynamic height, temperature, salinity, chlorophyll, zooplankton volume, geostrophic currents, and eddies as independent variables. Dynamic height explained more variance than any other variable in models of sardine and anchovy spawning habitat. Together temperature, salinity, and chlorophyll accounted for 80–95% of the dynamic height effect, emphasizing the importance of the first two mechanisms. However, dynamic height remained statistically significant in the models of anchovy and jack mackerel spawning habitat after considering the effects of all other variables. Dynamic height shows promise as an ecological indicator of spawning habitat, because it integrates the effects of multiple oceanic variables, can be remotely sensed, and is predicted by ocean circulation models.

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Bax, NJ, Appeltans W, Brainard R, Duffy JE, Dunstan P, Hanich Q, Davies HH, Hills J, Miloslavich P, Muller-Karger FE, Simmons S, Aburto-Oropeza O, Batten S, Benedetti-Cecchi L, Checkley D, Chiba S, Fischer A, Garcia MA, Gunn J, Klein E, Kudela RM, Marsac F, Obura D, Shin YJ, Sloyan B, Tanhua T, Wilkin J.  2018.  Linking capacity development to GOOS monitoring networks to achieve sustained ocean observation. Frontiers in Marine Science. 5   10.3389/fmars.2018.00346   AbstractWebsite

Developing enduring capacity to monitor ocean life requires investing in people and their institutions to build infrastructure, ownership, and long-term support networks. International initiatives can enhance access to scientific data, tools and methodologies, and develop local expertise to use them, but without ongoing engagement may fail to have lasting benefit. Linking capacity development and technology transfer to sustained ocean monitoring is a win-win proposition. Trained local experts will benefit from joining global communities of experts who are building the comprehensive Global Ocean Observing System (GOOS). This two-way exchange will benefit scientists and policy makers in developing and developed countries. The first step toward the GOOS is complete: identification of an initial set of biological Essential Ocean Variables (EOVs) that incorporate the Group on Earth Observations (GEO) Essential Biological Variables (EBVs), and link to the physical and biogeochemical EOVs. EOVs provide a globally consistent approach to monitoring where the costs of monitoring oceans can be shared and where capacity and expertise can be transferred globally. Integrating monitoring with existing international reporting and policy development connects ocean observations with agreements underlying many countries' commitments and obligations, including under SDG 14, thus catalyzing progress toward sustained use of the ocean. Combining scientific expertise with international capacity development initiatives can help meet the need of developing countries to engage in the agreed United Nations (UN) initiatives including new negotiations for the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction, and the needs of the global community to understand how the ocean is changing.

Bird, JL, Eppler DT, Checkley DM.  1986.  Comparisons of herring otoliths using Fourier series shape analysis. Canadian Journal of Fisheries and Aquatic Sciences. 43:1228-1234.   10.1139/f86-152   AbstractWebsite

Numeric analysis of otolith morphology provides vital information to commercial fisheries concerning the age distribution, racial origin, and, to some extent, the environmental history of fish stocks. Conventional methods used to retrieve these data, though proven to be effective, are time consuming, susceptible to ambiguous interpretations, and only semiquantitative. Fourier shape descriptors, when used to analyze outlines of otolith silhouettes, represent a rapid, objective, semiautomated means of obtaining much of this information. Analysis of Fourier shape information derived from otoliths of juvenile and adult Alaskan herring and adult Northwest Atlantic herring show that otolith shape reflects differences in fish age and fish race. The shape of otoliths of juvenile fish are significantly different from those of adult fish. Few shape differences can be found, though, between otoliths from adult fish of different age within the same stock. Distinct differences exist between Atlantic and Alaskan adult otolith shapes. For some stocks, minor shape differences occur between left and right otoliths. Differences in otolith shape arising from sexual dimorphism are not apparent.

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Cambalik, JJ, Checkley DM, Kamykowski D.  1998.  A new method to measure the terminal velocity of small particles: A demonstration using ascending eggs of the Atlantic menhaden (Brevoortia tyrannus). Limnology and Oceanography. 43:1722-1727. AbstractWebsite

A new method, incorporating video, motion analysis, and a novel experimental apparatus, was used to measure the terminal velocity of particles. The method facilitated the investigation of treatment effects and maximized the number of measurements for each replicate, thus improving the statistics for a population of particles. The eggs of the Atlantic menhaden (Brevoortia tyrannus) were used to demonstrate the method by investigating the effects of salinity and stage of development on their ascent rate. Egg ascent rate was greatest at intermediate salinity (36.5 parts per thousand) and decreased in the late stage of embryonic development. We estimate eggs at oceanic salinities (>35.5 parts per thousand) in nature to ascend at 0.19-0.25 cm s(-1).

Checkley, DM, Asch RG, Rykaczewski RR.  2017.  Climate, anchovy, and sardine. Annual Review of Marine Sciences, Vol 9. 9:469-493., Palo Alto: Annual Reviews   10.1146/annurev-marine-122414-033819   Abstract

Anchovy and sardine populated productive ocean regions over hundreds of thousands of years under a naturally varying climate, and are now subject to climate change of equal or greater magnitude occurring over decades to centuries. We hypothesize that anchovy and sardine populations are limited in size by the supply of nitrogen from outside their habitats originating from upwelling, mixing, and rivers. Projections of the responses of anchovy and sardine to climate change rely on a range of model types and consideration of the effects of climate on lower trophic levels, the effects of fishing on higher trophic levels, and the traits of these two types of fish. Distribution, phenology, nutrient supply, plankton composition and production, habitat compression, fishing, and acclimation and adaptation may be affected by ocean warming, acidification, deoxygenation, and altered hydrology. Observations of populations and evaluation of model skill are essential to resolve the effects of climate change on these fish.

Checkley, DM, Barth JA.  2009.  Patterns and processes in the California Current System. Progress in Oceanography. 83:49-64.   10.1016/j.pocean.2009.07.028   AbstractWebsite

The California Current System (CCS) is forced by the distribution of atmospheric pressure and associated winds in relation to the west coast of North America. In this paper, we begin with a simplified case of winds and a linear coast, then consider variability characteristic of the CCS, and conclude by considering future change. The CCS extends from the North Pacific Current (similar to 50 degrees N) to off Baja California, Mexico (similar to 15-25 degrees N) with a major discontinuity at Point Conception (34.5 degrees N). Variation in atmospheric pressure affects winds and thus upwelling. Coastal, wind-driven upwelling results in nutrification and biological production and a southward coastal jet. Offshore, curl-driven upwelling results in a spatially large, productive habitat. The California Current flows equatorward and derives from the North Pacific Current and the coastal jet. Dominant modes of spatial and temporal variability in physical processes and biological responses are discussed. High surface production results in deep and bottom waters depleted in oxygen and enriched in carbon dioxide. Fishing has depleted demersal stocks more than pelagic stocks, and marine mammals, including whales, are recovering. Krill, squid, and micronekton are poorly known and merit study. Future climate change will differ from past change and thus prediction of the CCS requires an understanding of its dynamics. Of particular concern are changes in winds, stratification, and ocean chemistry. (C) 2009 Elsevier Ltd. All rights reserved.

Checkley, DM.  1980.  Food limitation of egg production by a marine, planktonic copepod in the sea off Southern California. Limnology and Oceanography. 25:991-998. AbstractWebsite

The in situ rate of egg production (B) and female size of Paracalanus parvus, a particle-grazing copepod, water temperature, and the concentrations of chlorophyll a and particulate nitrogen were measured in 31 collections from the euphotic zone of the sea off southern California. B was correlated positively with chlorophyll a and female size and negatively with temperature. A multiple regression of log B on chlorophyll a, particulate nitrogen, female size, and temperature accounts for44% ofthe variationin log B. B was predicted best by an empirical function of food concentration when the food available in nature was considered to be phytoplankton rather than of all types of particulate matter >5 µ.An index of immediate food limitation was derived from laboratory data as a function of food concentration. When applied to extensive measurements of chlorophyll a in the euphotic zone, this index indicates that Paracalanus was often food limited and that food limitation increased along an onshore-offshore transect. Paracalanus was rarely food limited in Santa Monica Bay.

Checkley, DM, Ortner PB, Settle LR, Cummings SR.  1997.  A continuous, underway fish egg sampler. Fisheries Oceanography. 6:58-73.   10.1046/j.1365-2419.1997.00030.x   AbstractWebsite

We describe a method to sample the highly contagious distribution of pelagic fish eggs. CUFES, the continuous, underway fish egg sampler, consists of a submersible pump, concentrator, electronics and sample collector. This system operates continuously and under nearly all sea conditions, providing a real-time estimate of the volumetric abundance of pelagic fish eggs at pump depth, usually 3 m. CUFES-derived estimates of volumetric abundance agree well with those from nets towed at pump depth and with areal abundance estimated from vertically integrated plankton tows. CUFES has been used successfully to sample the eggs of menhaden, pinfish, sardine, and anchovy off the coasts of the eastern and western United States and South Africa. Two large patches of eggs of the Atlantic menhaden were sampled off North Carolina in winter 1993-94, had a linear scale of 5-10 km, and were found in waters between the Gulf Stream and mid-shelf front. Spawning location may he related to bathymetry. CUFES is now being used to estimate spawner biomass by the daily egg production method. An optical plankton counter provided accurate estimates of the number of Atlantic menhaden eggs sample by CUFES.

Checkley, D.  2009.  Climate change and small pelagic fish. :1onlineresource(xvii,372p.)ill.,maps.., Cambridge, UK ; New York: Cambridge University Press,   10.1017/CBO9780511596681   Abstract
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Checkley, DM, Raman S, Maillet GL, Mason KM.  1988.  Winter Storm Effects on the Spawning and Larval Drift of a Pelagic Fish. Nature. 335:346-348.   10.1038/335346a0   AbstractWebsite

Recruitment for many marine organisms depends on survival and transport of eggs and larvae from spawning grounds to nursery areas1. We investigated the effects of winter storms and the Gulf Stream on the spawning, development and drift of the Atlantic menhaden, Brevoortia tyrannus, which spawns offshore2 and metamorphoses in estuaries3. Spawning was maximal during storms in water upwelled near the western edge of the Gulf Stream. Eggs and larvae drifted shoreward with abundant food in the warm surface stratum of a density-driven circulation maintained by the large sea–air heat flux. We suggest that the Atlantic menhaden and other species have evolved to reproduce in winter near warm boundary currents, including the Gulf Stream and Kuroshio, as a result of physical conditions that permit the rapid development and shoreward drift of their eggs and larvae, with consequent high recruitment and fitness.

Checkley, DM, Dotson RC, Griffith DA.  2000.  Continuous, underway sampling of eggs of Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) in spring 1996 and 1997 off southern and central California. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 47:1139-1155. AbstractWebsite

Eggs of the northern anchovy and Pacific sardine were sampled at 3 m depth using the Continuous, Underway Fish Egg Sampler (CUFES) during two cruises off southern and central California in March and April 1996 and 1997. Simultaneous measurements were made of seawater temperature and salinity. Real-time AVHRR satellite images of sea surface temperature were processed onshore and transmitted to the ship at sea. Sardine and anchovy eggs were identified and counted live, at sea, and again ashore, preserved. A total of 2129 CUFES samples were collected during 41 d at sea and contained 62,409 sardine and 15,123 anchovy eggs. Sardine eggs were widespread and abundant in both cruises (mean concentrations: 5.2 and 5.1 eggs m(-3)) at and shoreward of the eastern boundary of the California Current. Anchovy eggs were found primarily inshore in the Southern California Eight and were less abundant (0.4 and 1.0 eggs m(-3), respectively, for the two cruises). Temperature-salinity plots indicated distinct separation of the spawning habitat of these two species and consistency in habitat between cruises in successive years. The distributions of sardine eggs and euphausiids collected by CUFES were complementary in space and time. (C) 2000 Elsevier Science Ltd. All rights reserved.

Checkley, DM, Entzeroth LC.  1985.  Elemental and isotopic fractionation of carbon and nitrogen by marine, planktonic copepods and implications to the marine nitrogen cycle . Journal of Plankton Research. 7:553-568.   10.1093/plankt/7.4.553   AbstractWebsite

Particle-grazing copepods, primarily Temora longicornis and T. stylifera, and seawater with natural particles were collected from the northwest Gulf of Mexico. Control and ammonium-enriched aliquots of seawater were incubated in triplicate for 2 days, copepods added and the incubation continued for 2 days. Analyses were made of dissolved nutrients (nitrate, ammonium and phosphate), suspended particles (chlorophyll a and phaeopigments, C, N, τ13C, τ15N), and copepod bodies and feces (C, N, τ13C, τ15N) and the rates of egg and feces production were estimated. Primary production Δchlorophyll a, C, N) was enhanced by N enrichment, indicating its initial N limitation. The rates of egg and feces production were greatest for copepods in N-enriched seawater, indicating food-limited ingestion and egg production. Elemental (C:N) and isotopic (τ13C, τ15N) fractionation by copepods occurred following ingestion of suspended particulate matter (spm) and during the production of tissue (b) and feces (f): C:Nf>C:Nspm >C:Nb, τ13Cb>τ13Cf>τ13Cspm, and τ15Nf>τ15Nb>τ15Nspm. In a second experiment, N-enriched and N-deficient phytoplankton were fed to Acartia tonsa and again C:Nf>C:Nspm>C:Nb. These data indicate that copepods in the present study (i) used nitrogen more efficiently than carbon for tissue production and (ii) produced tissue and feces enriched and excreta depleted in 13C and 15N relative to the suspended particulate matter. The implications of these results to the marine nitrogen cycle are discussed.

Checkley, DM, Dickson AG, Takahashi M, Radich JA, Eisenkolb N, Asch R.  2009.  Elevated CO2 Enhances Otolith Growth in Young Fish. Science. 324:1683-1683.   10.1126/science.1169806   AbstractWebsite

A large fraction of the carbon dioxide added to the atmosphere by human activity enters the sea, causing ocean acidification. We show that otoliths (aragonite ear bones) of young fish grown under high CO2 (low pH) conditions are larger than normal, contrary to expectation. We hypothesize that CO2 moves freely through the epithelium around the otoliths in young fish, accelerating otolith growth while the local pH is controlled. This is the converse of the effect commonly reported for structural biominerals.

Checkley, DM.  1982.  Selective feeding by Atlantic herring (Clupea harengus) larvae on zooplankton in natural assemblages. Marine Ecology-Progress Series. 9:245-253.   10.3354/meps009245   AbstractWebsite

The hypothesis that larval herring Clupea harenyus select food by type as well as size was tested in laboratory experiments. Herring larvae were reared at 7 to 9°C on wild zooplankton. The percentage of herring larvae with food at day's end increased from 4 % (4 d) to 68 % (9 d) and averaged 83 % for larvae 25 to 74 d old. Larval herring selected particles according to type as well as size; this selectivity varied with larval age and hence size. Copepod nauplii and copepodites were preferred by larvae of all sizes. Among copepodites, Pseudocalanus sp, and Oithona sp. were preferred by smaller and larger larvae, respectively, while Acartia sp. was rarely ingested, even when of acceptable size. Mollusc veligers comprised a significant portion of the diet of young (4 to 24 d) larvae but were actively rejected by older larvae even when perceived and of acceptable size. Particles smaller than the largest acceptable size were consistently preferred, atypical of predation by vertebrates. These results indicate that larval herring select prey according to type as well as size and that this behavior is acquired through experience.

Checkley, DM, Miller CA.  1989.  Nitrogen isotope fractionation by oceanic zooplankton. Deep-Sea Research Part a-Oceanographic Research Papers. 36:1449-1456.   10.1016/0198-0149(89)90050-2   AbstractWebsite

The ratio of 15N:14N for particulate matter suspended in oceanic, surface waters is high after recent nitrate depletion and low in the stable, oligotrophic ocean. We hypothesize that zooplankters and other pelagic heterotrophs produce 15N-depleted ammonium and 15N-enriched particulate matter that are, respectively, recycled in and exported from the euphotic zone and thus cause the low values of 15N:14N in oligotrophic seas. Heretofore, this pattern was attributed to nitrogen-fixation by the phytoplankton.We measured the ratio of 15N:14N in the bodies and excreted ammonium of zooplankters from the northwest Pacific Ocean and compared these values to the ratio of 15N:14N for subeuphotic, dissolved nitrate. We report that oceanic zooplankton excrete ammonium that is isotopically light relative to their bodies and subeuphotic nitrate. These results are consistent with our hypothesis and the view that the phytoplankton of oligotrophic seas is nourished primarily by nitrogen recycled within the euphotic zone. Nitrate injected into the euphotic zone may be manifest and hence detected by an increase of the ratio 15N:14N for the particulate matter suspended therein.

Checkley, DM, Dagg MJ, Uye S.  1992.  Feeding, excretion and egg production by individuals and populations of the marine, planktonic copepods, Acartia spp. and Centropages furcatus. Journal of Plankton Research. 14:71-96.   10.1093/plankt/14.1.71   AbstractWebsite

Diel variations in vertical distribution, gut pigment content, ammonium excretion and egg production were investigated for adult females of Acartia erythraea and A. pacifica in the vertically mixed Inland Sea of Japan and Centropages furcatus in the stratified, neritic Gulf of Mexico. Gut pigment content and egg production rate were maximal at night and ammonium excretion was maximal during the daytime. Neither A. erythraea nor A. pacifica adult females showed an apparent diel migration, but the former were highly concentrated in the sur-face layer during the afternoon. In contrast, C. furcatus adult females showed a clear diel migration, residing immediately above the bottom during the daytime and being concentrated between 10 and 25 m depth during the night-time. Individual-based data on gut content and excretion and egg production rates were combined with vertical-distribution data to calculate population values. In the Inland Sea of Japan, the resultant pattern for Acartia spp. reflected the diel variation in physiological rates and even distribution of adult females, except for the afternoon, surface aggregation of A. erythraea. In the Gulf of Mexico, the pattern for C. furcatus reflected largely the diel variation in each rate process and the heterogeneous distribution of adult females in the water column. Elevated nocturnal feeding activity of these copepods may be due to an endogenous rhythm. The daytime maximum in ammonium excretion and night-time maximum in egg production rate indicated approximate half-day and day time lags, respectively, after the intake of food until its conversion into dissolved excreta and released eggs.

Checkley, DM.  1984.  Relation of growth to ingestion for larvae of Atlantic herring Clupea harengus and other fish. Marine Ecology-Progress Series. 18:215-224.   10.3354/meps018215   AbstractWebsite

Larvae of Atlantic herring Clupea harengus were reared on wild plankton and Artemia salina nauplii in the laboratory at 7 to 9°C for 95 d. Between ages of 20 and 38 d, larvae were fed only Artemia nauplii and the specific rates of ingestion and growth were measured and compared. Relations of rate and efficiency of growth to ingestion were similar in terms of carbon and nitrogen. Growth was linearly related to ingestion (r2= 0.89, n = 9). Starved larvae lost mass at a specific rate of 0.03 d^-1 (3% d^-1) until death at 14 d. A specific ingestion rate of 0.04 d^-1 was required to balance defecation and metabolism. Gross growth efficiency (growth rate/ingestion rate) rose from -1.2 at a low ingestion rate (0.015 d^-1) to 0.4 at the greatest observed ingestion rate (0.11 d^-1) . Condition factor (dry weight length^-3) was significantly related to both ingestion rate and length (r2 = 0.69, n = 20).These results, combined with those for other fish larvae, indicate an asymptotic relation between rates of growth and ingestion such that gross growth efficiency is maximal (0.4) at intermediate ingestion rate. Fish larvae surviving in the sea appear to maximize their ingestion rate and thus grow rapidly but with a reduced efficiency.

Checkley, DM.  1980.  The egg production of a marine panktonic copepod in relation to its food supply - Laboratory studies. Limnology and Oceanography. 25:430-446. AbstractWebsite

Egg production by Paracalanus parvus, a particle-grazingcopepod, was investigated in relation to its food supply. The concentration of available food (P) and the rates of ingestion (I) and egg production (B) were measured simultaneously at intervals of 6 h to 2 d for periods of 2-10 d. Concentration, chemical composition (carbon and nitrogen), and species of phytoplankton were experimental variables.Egg production was related to the food ingested during the previous day. For one food type, I and B were rectilinear functions of P. The average maximum rates of ingestion and egg production were 1.1 µg N ∙ female^-1 ∙ d^-1 and 53 eggs ∙ female^-1 ∙d^-1, equivalent to specific rates of 1.5 and 0.37 d^-1. B was proportional to I below a critical ingestion rate, Ic, and independent of I above Ic. For I < Ic, the gross efficiency of egg production (B ∙ I^-1) in terms of nitrogen was 0.37 while in terms of carbon it was a hyperbolic function of the ratio of C:N in the food, ranging between 0.41 (C:Nfood= 4.0) and 0.15 (C:Nfood= 11). For I >Ic, B ∙ I^-1 declined in terms of both carbon and nitrogen.These results, together with the ratio of C:N in particulate matteri n the sea off southern California, suggest that nitrogen (hence protein) potentially limits egg production by adult female Paracalanus and that ingested carbon is used inefficiently.

Checkley, DM, Davis RE, Herman AW, Jackson GA, Beanlands B, Regier LA.  2008.  Assessing plankton and other particles in situ with the SOLOPC. Limnology and Oceanography. 53:2123-2136.   10.4319/lo.2008.53.5_part_2.2123   AbstractWebsite

We combined a Sounding Oceanographic Lagrangian Observer float with a Laser Optical Plankton Counter (LOPC) and a fluorometer to make an autonomous biological profiler, the SOLOPC. The instrument senses plankton and other particles over a size range of 100 mm to 1 cm in profiles to 300 m in depth and sends data ashore via satellite. Objects sensed by the LOPC include aggregates and zooplankton, the larger of which can be distinguished from one another by their transparency. We hypothesized that the diel production of particles and their loss by sinking and grazing are reflected in the change of the particle distribution. We present data from four deployments of the SOLOPC off California. Particle volume was maximal at the base of the surface mixed layer and correlated with chlorophyll a fluorescence. In a 3-d deployment in 2005, particle volume was greatest in the early evening and smallest in the morning, and average particle size increased with depth. Eigenvector analysis of the particle volume distribution as a function of diameter for each of the deployments yielded size peaks characteristic of planktonic crustaceans. Ship-based measurements showed that the abundance of opaque particles of 1.1-1.7 mm equivalent spherical diameter was positively correlated with copepods of this size and simultaneously collected in nets. This relationship was used with SOLOPC data to estimate the distribution of large copepods, which were most abundant beneath the depth of maximal particle flux, estimated from particle size and published sinking rates. Our data are consistent with a model with diel production of particles and their loss by sinking and grazing.

Checkley, DM, Lindegren M.  2014.  Sea surface temperature variability at the Scripps Institution of Oceanography Pier. Journal of Physical Oceanography. 44:2877-2892.   10.1175/jpo-d-13-0237.1   AbstractWebsite

Sea surface temperature (SST) has been measured from near the end of the Scripps Institution of Oceanography (SIO) pier daily since 1916. It is one of the world's longest instrumental time series of SST. It is widely used in studies of climate and marine ecosystems and in fisheries management. The authors hypothesized that a discontinuity exists in 1988, when the old pier was replaced with the present pier. A regression of annual-mean SST at SIO (SSTSIO) on the Pacific decadal oscillation index for 1916-87 was used to predict annual-mean SST (SSTSIO,PDO) for 1916-present. The residual (ResSST(SIO) = SSTSIO - SSTSIO,PDO) time series shows a positive discontinuity in 1988, when the present SIO pier was first used to measure SSTSIO. No discontinuity in 1988 was observed for ResSST at 12 other shore stations or in nearby waters. Use of the first principal component of other shore station time series of annual-mean SST as the predictor yields similar results. SSTSIO measured over 3 days shows a diel cycle and short-term variability consistent with rip current transport of warm surf-zone water to the end of the SIO pier. This study hypothesizes that rip current transport increased with the change from the old to the present pier and contributed to the observed discontinuity in SIO pier SST. The authors estimate an artifact of about +0.45 degrees C due to both rapid (1988 pier change) and gradual processes. Adjusting the SIO pier SST time series for this artifact reduces the long-term trend from +1.1 degrees to +0.6 degrees C century(-1), consistent with the global rate of change of SST over the past century.

Checkley, DM, Uye S, Dagg MJ, Mullin MM, Omori M, Onbe T, Zhu MY.  1992.  Diel variation of the zooplankton and its environment at neritic stations in the Inland Sea of Japan and the north-west Gulf of Mexico. Journal of Plankton Research. 14:1-40.   10.1093/plankt/14.1.1   AbstractWebsite

Diel variations in the zooplankton and its environment were investigated at two, contrasting neritic stations. The first (BG-1), in the Inland Sea of Japan, was mixed and eutrophic, while the second (GM-1), in the north-west Gulf of Mexico, was stratified and oligotrophic. Intensive studies were conducted at each station in late summer for 2-3 days. Dissolved nutrients and the particulate matter were evenly distributed in time and space at BG-1, but were variable, and often maximal at depth in a nepheloid layer, at GM-1. For each station, approximately 20 categories of zooplankton were enumerated in samples collected with a plankton pump and retained on approximately 100-mu-m mesh filters, In general, the zooplankton at BG-1 exhibited little diel variation in abundance and distribution. By contrast, most types of zooplankton at GM-1 performed diel vertical migrations, though primarily within the lower half of the water column between the thermocline and nepheloid layer. Significantly, similar taxa and stages did not always behave similarly in these two, differing environments, nor did the zooplankton at GM-1 tend to aggregate at the depths of maximal particle abundance or primary productivity. We suggest that studies of diel variation of the distribution and abundance of the zooplankton often require more intense sampling, in time and space, in environments which are stratified rather than mixed.

Checkley Jr., DM.  2000.  Michael M. Mullen: A biography. PICES Press. 8:13-17. Abstract
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Checkley Jr., DM, Cooper T, Lennert C.  1996.  Plankton pattern within and below the surface mixed layer. EOS Trans. AGU. 76:198. Abstract
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