Clearance rates on natural assemblages of aloricate, phagotrophic ciliates (20 to 100 pm) were measured for calanoid copepods in Oregon, USA, coastal waters. Experiments were conducted prior to and throughout the 1991 upwelling season in an effort to determine the trophic significance of cihates as copepod prey in a system often dominated by large phytoplankton. Copepods cleared ciliates at higher rates than they cleared phytoplankton, except during upwelling-induced diatom blooms. Clearance rates on ciliates (nll copepod-' h-') were measured for Calanus pacificus (12.6 to 32.4), Pseudocalanus sp. (4.8 to 7.4) and Centropages abdominalis (1.2 to 7.1). The highest clearance rates on chates were measured when the phytoplankton standing stock was < 5 pg chl a I-' No detectable clearance of ciliates was measured for Acartja longiremis or C. pacificus during upwelling bloom events (45 pg chl a I-'). Ciliate biomass ranged from 3 to 32 pg C I-' and was significantly less than phytoplankton biomass (100 to 2200 pg C I-') on all dates. During non-upwelling months and between diatom blooms, ciliates contributed 16 to 100% of the estimated carbon ingested by copepods. Calculated ingestion of ciliate carbon (pg C copepod-' d-') averaged 6.5 (e2.4) for C. pacifjcus, 4.6 (* 1.1) for Pseudocalanus sp. and 0.7 (k0.4) for C. abdominalis. Ingestion of ciliates alone provided enough carbon to meet the basic respiration requirements of C. pacificus and Pseudocalanus sp. in January and February respectively. Estimates of predation, based on average copepod densities, indicate 25 to 45 % of the phagotrophic ciliate population is cleared from surface waters per day.

Grazing on chlorophyll by microzooplankton (<200 •um) and copepods was measured in the mixed layer of the high-latitude North Atlantic Ocean during May and August 1991. No significant grazing by microzøoplankton occurred in May during a spring bloom dominated by colonial Phaeocystis pouchettii and Nitzschia spp. As the bloom declined, the size distribution of chlorophyll shifted from dominance by the > 20 •um chlorophyll fraction to dominance by the <20 chlorophyll fraction. The impact of grazing by microzooplankton increased as the bloom declined, with microzooplankton consuming 100% of potential daily chlorophyll production following the bloom. In August,.when the phytoplankton was dominated by the <20 #m chlorophyll fraction, m•cr0zooplankton consumed 37-53% (mean = 41%_+11% s.d.)'of potential daily chlorophyll production. Averaged over all experiments, microzooplankton grazing accounted for 81% of daily chlorophyll production. The grazing impact of Calanus finmarchicus stages C4 and C5, which dominated mesozooplankton biomass in the upper euphotic zone in both spring and late summer, was concentrated on chlorophyll > 20/tin in both seasons; C. f in mar c h ic u s did not consume significant amounts of chlorophyll < 20 •um in either season. Compared to the microzooplankton, copepods did not consume a significant fraction of total chlorophyll in either season, accounting for only -1% of daily chlorophyll production. Introduction The objective of this study was to evaluate losses of chlorophyll due to grazing by microzooplankton and mesozooplankton in the mixed layer of the high-latitude North Atlantic Ocean under contrasting biological and hydrographic conditions during spring and summer. The research was conducted on RV Endeavor cruises EN224-3 and EN227 in spring and late summer 1991 under the aegis of the Marine Light Mixed Layers (MLML) Accelerated Research Initiative, a multidisciplinary effort focused on the biological, physical and optical dynamics of the mixed lay_cr. The MLML study site was occupied t'or 8 days •n May 1991 and 9 days in August/Scptcmber 1991. Paper number 94JC00983 0148-0277!95!94JC-00983505.00 tic Front, an area characterized by extreme seasonal forcing of biology and hydrography. Convective cooling of the water column during winter produces adccp mixed layer of at least several hundred meters, which provides new nutrients to the system [Robinson et al., 1979; Plueddemann et al., this issue]. Irradiance and phytoplankton standing stocks are low during winter when phytoplankton growth is believed to be very low. With the onset of stratification, typically in April, standing stocks of chlorophyll increase IWil!iams and Hopkins, 1974; Plueddemann et al., this issue; Stramska et al., this issue], and a strong diatom bloom reaching 2-5/•g L '•. Calanus finmarchicus and other copepod species appear in the euphotic zone at this time, but their grazing appears to have little impact on the bloom [Dam et al., 1993; Morales et al., 1991; Weeks et al., 1993]. Transition to the summer phytoplankto...

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The mesozooplankton in the upper 100 m at 59øN, 21øW were dominated by the copepodite stages of Calanus finmarchicus in both May and August 1991. Abundance of C. finmarchicus in the upper 20 m of the water column was 800 m -3 in May and 200 m -3 in August. Although hydrographic conditions changed from well mixed to stratified between May and August, the fine-scale vertical distribution pattern of C. finmarchicus was essentially the same during these two surveys of the Marine Light-Mixed Layers site. Copepodite stage five (CV) comprised a larger fraction of the population in August compared to May, however. Gut evacuation experiments with C. finmarchicus indicated that late copepodite and adult female life stages had evacuation rates of approximately 4 % h 4 in both May and August. Although these evacuation rates are consistent with others measured for Calanus, the relatively low biomass in the upper 100 m resulted in anestimated daily grazing impact by Calanus of less than 5 % of the phytoplankton standing stock in May, and less than 1% in August. The ingestion rates we measured suggest that the total grazing impact of all mesozooplankton grazers is less than 10% of daily primary production. These relatively low ingestion rates on phytoplankton provide these copepods with less than half of the total daily carbon intake required to balance estimated rates of respiration and growth in the field. In order to balance these metabolic costs, we estimate that the mesozooplankton would need to ingest the equivalent of at least 100% of the estimated microzooplankton/protist daily production. Introduction Plankton studies conducted in the North Atlantic over the past several decades have been the source of much of our knowledge about the seasonal cycles of phytoplankton and zooplankton abundance [Matthews, 1969; Miller et al., 1991; Williams and Lindley, 1982; Williams, 1988], the horizontal gradients of species distributions [Fleminger and Hulsemann, 1977; Colebrook, 1979], as well as the vertical distribution patterns of dominant species [Grice and Hulsemann, 1965; Longhurst and Williams, 1979]. Recent investigations of the spring bloom in the temperate North Atlantic have increased our knowledge of production and grazing processes [Burkill eta/., 1993; Dam et al. , 1993; Morales et al., 1991], but few data are available which describe zooplankton distributions and grazing processes on vertical scales of 25 m or less. Cruises to the Marine Light-Mixed Layers (MLML) site (59øN, 21øW) in May and August of 1991 gave us the opportunity to evaluate the finescale distribution and grazing of the copepods which dominated the upper 100 m of the water column. Smith [1988] sampled five depth strata within the upper 200 m of the Fram Strait, and found that Calanus finmarchicus, Pseudocalanus spp., and Metridia spp. dominated the copepod assemblage in the upper 200 m in late spring. Time series sampling from Ocean Weather Station India (59øN, 20øW) in the early 1970's showed that the zooplankton were dominated by Calanus finmarchicus...

What are the enduring effects of community‐based conflict resolution processes? According to the research reported here, lessons participants learn in conflict resolution processes disseminate to their communities; secondly, such dissemination can be measured by content analysis of participants’ constituent organization newsletters. The authors illustrate their findings with a case study of the New Community Meeting conflict resolution model (NCM), implemented 1997–98 in an Oregon community to address business‐environmental conflict over growth and sustainable development. Content analysis of business and environmental newsletters over 21 months, including before and after NCM, shows increasing positive and decreasing negative references to former adversaries over the period, together with advocacy for collaboration. The authors frame this study using social exchange theory, and conclude that this theoretical paradigm fits conflict resolution and consensus‐building processes well.