An upper limit on gas production from 3200 Phaethon

Asteroid 3200 Phaethon resembles a comet in some ways, including a highly-eccentric orbit (e∼0.89) and a strong associated meteor shower (the Geminids). Yet this object has never been observed to exhibit any cometary activity, i.e., gas production. We observed 3200 Phaethon with the Caltech Submillimeter Observatory on two occasions, once while it was near its closest approach to Earth as it neared perihelion, and another while it was further from Earth post-perihelion. Observations of the J=2→1 and J=3→2 rotational transitions of ¹²CO, typically strong lines in comets and indicative of gas production, yielded no detection. Upper limits on the ¹²CO production of 1.8×¹⁰²⁸ and for Phaethon were determined on these two occasions.     

Fish biomass size spectra in Chesapeake Bay

Biomass size spectra of pelagic fish were modeled to describe community structure, estimate potential fish production, and delineate trophic relationships in Chesapeake Bay. Spectra were constructed from midwater trawl collections each year in April, June–August, and October 1995–2000. The size spectra were bimodal: the first spectral dome corresponded to small zooplanktivorous fish, primarily bay anchovyAnchoa mitchilli; the second dome consisted of larger fish from several feeding guilds that are supported by multiple prey-predator linkages. Annual production estimates of pelagic fish, derived from a mean production to biomass ratio, varied nearly three-fold, ranging from 162 × 109 kcal (125 × 103 tons) in 1996 to 457 × 109 kcal (352 × 103 tons) in 2000. Seasonally, the biomass level and mean individual sizes of fish in the first dome increased from April to October, while the biomass level of the second dome was relatively stable. Regionally, biomass levels in the second dome were higher than biomasses in the first dome for the upper and lower Bay, but were minimal in the middle Bay where seasonal and episodic hypoxia occurs. To test a benthic-pelagic coupling hypothesis that could explain the higher biomass in the second domes for the lower and upper Bay, a cyclic size-spectrum model was fit that included only species in the zooplanktivorous-piscivorous fish guilds. The mean, normalized slope equaled ?1, indicating that zooplanktivorous fish may support piscivore production, but that a benthic-pelagic linkage is required to fully support fish production in the second dome. Interannual variability in slopes and intercepts of modeled size spectra was related to salinity, recruitment level of bay anchovy, and the primary axis of a correspondence analysis (salinity effect) on fish community structure. The spectral slope and intercept of normalized spectra were lowest in 1996, a near-record wet year. Results suggest that fish size spectra can be developed as useful indicators of ecosystem state and response to perturbations, especially if prey-predator relationships are explicitly represented.     

市场化配置方式出让用海的海域使用论证内容优化的探索

海域使用论证是取得海域使用权的一项基础工作,现行的《海域使用论证技术导则》主要适用于以行政配置方式申请用海的海域使用论证,对于市场化配置方式出让海域使用权,因为委托业主的不同和对海域利用方案的不确定性,对海域使用论证的关注点也有所不同,文章讨论对市场化配置方式出让用海的海域使用论证内容进行适当优化,主要从项目用海基本情况、用海资源环境影响分析和用海合理性分析等方面优化进行初步探讨,并提出完善海域市场化配置制度和相关的技术规范的建议。     

无居民海岛资源环境承载力多目标规划模型初探

资源环境承载力是衡量无居民海岛发展是否可持续的重要标尺,在现有的承载力条件下如何设计合理的海岛规划方案,如何分配各资源环境成为海岛健康发展的关键。文章构建资源环境承载力多目标规划方法,以海岛旅游人口和经济总量最大化为目标,从资源、生态、环境的有限性或限制性作为模型约束条件,以期为海岛规划提供技术方法。     

假设开发法在海域使用权价值评估中的应用 ——以游艇码头用海为例

随着国家资源管理体制改革的加快,海域资源的市场化配置程度不断提高,而海域使用权价格评估是其基础工作。在诸多评估方法中,假设开发法把在开发和未开发海域假设为已完工状态而进行评估,非常适宜于当前海域市场化出让前的状态,已经成为目前海域使用权评估领域最常用的评估方法。文章选取A市游艇码头项目用海为例,利用假设开发法详细测算了该宗海域价格,并通过对测算过程和测算结果进行分析,探讨假设开发法在海域价格评估领域的应用及局限,对进一步完善海域使用权价格评估工作具有积极意义。     

Seasonality of occurrence,foods and food preferences of ichthyoplankton in Biscayne Bay,Florida

Ichthyoplankton and microzooplankton were collected twice monthly for one year at a single station in Biscayne Bay, Florida. Based on approximate 10-m³, 333-μm mesh bongo net samples, the mean annual densities were 17·7 m^?3 and 1·8 m^?3 for fish eggs and larvae, respectively. Ichthyoplankton was most abundant in spring-summer. The most common fish larvae were bay anchovy (Anchoa mitchilli), spotted dragonet (Callionymus pauciradiatus), thread herring (Opisthonema oglinum) and gobies (Gobiidae), which comprised 50% of all larvae collected. A comparison of 35-μm and 333-μm mesh, bongo net collections revealed that mean densities of fish larvae were 8·5 times higher in the smaller mesh. The most abundant microzooplankton, based on 35-μm bongo net collections, were copepod nauplii, <100 μm in width, which averaged 90·41^?1 and tintinnids which averaged 168·51^?1. The mean density of microzooplankton <100 μm wide, potentially suitable food for first-feeding fish larvae, was 104·91^?1, exclusive of tintinnids, and 273·41^?1 including tintinninds. Excepting tintinnids, seasonal variability in microzooplankton abundance was low relative to that for ichthyoplankton. High microzooplankton densities, combined with low seasonal variability, indicated that feeding conditions for fish larvae were usually good in Biscayne Bay. Copepods, especially nauplii, were the predominant food of fish larvae (71% of all food items). Only mollusc veliger larvae (18% of all food items) were highly preferred prey but they were a small component of most larval fish diets. Average width of prey eaten by first-feeding larvae was 74 μm. Prey size increased in relation to larval length.     

Spatio-temporal Variability in Larval-Stage Feeding and Nutritional Sources as Factors Influencing Striped Bass (Morone saxatilis) Recruitment Success

Prey availability and feeding success affect survival of larval striped bass (Morone saxatilis) in Chesapeake Bay and contribute to the >30-fold interannual recruitment variability. Gut contents and stable isotope analyses (δ¹⁵N and δ¹³C) were conducted on striped bass larvae to evaluate sources of nutrition in 2007 and 2008, years of high and poor recruitment, respectively. Ichthyoplankton and zooplankton were surveyed in the upper Chesapeake Bay, in proximity to the estuarine turbidity maximum and associated salt front. Feeding incidence and numbers of prey per gut were similar in both years and varied in relation to the salt front. The primary prey in each year was the estuarine copepod Eurytemora affinis. Substantial consumption of the freshwater cladoceran Bosmina spp. also occurred, especially up-estuary of the salt front in 2007, demonstrating that secondary prey are important to larval diets in some years. Stable isotope analysis of yolk sac and feeding-stage larvae of striped bass revealed an ontogenetic shift from maternal stable isotope signatures to those indicative of prey source. Feeding-stage larvae from up-estuary locations had the most negative δ¹³C values, indicating a relatively high terrestrial carbon source in prey. Spatio-temporal variability in δ¹⁵N signatures of larvae followed similar trends of δ¹⁵N variability in zooplankton prey with the highest δ¹⁵N values up-estuary of the salt front and estuarine turbidity maximum. A stable isotope analysis on archived striped bass larvae collected in 1998 and 2003, years of moderate and high recruitment, respectively, expanded the documented range of isotope signatures but did not clearly distinguish effects of nutritional sources on recruitment.