Effect of time on the natural regeneration of salt marsh

Abstract. The effect of time on natural regeneration of two salt marshes was studied in relation to plant and edaphic factors. The study was carried out in two naturally restoring salt marshes, differing in restoration time, in Txingudi (Bay of Biscay). After 20 yr, the younger salt marsh had the same plant species richness and high species similarity as a 35 yr old salt marsh (17 and 16, respectively, similarity index = 0.9), but both sites had lower species richness and similarity than a nearby natural salt marsh (36 plant species and similarity indices of 0.45 with the 35 yr old marsh and 0.46 with the 20 yr old marsh). Plant species present in the two recovering salt marshes followed a similar distribution pattern in relation to organic matter, conductivity and moisture content although this zonation differed from the natural salt marsh. The range of edaphic factors measured was also similar, but differed from those in the natural salt marsh. The process of plant species recolonization and spatial distribution might be delayed by a low probability of species arrival and by the time need for the restoration of hydrologic and edaphic factors. This study supports the necessity of long‐term monitoring in measuring coastal salt marsh restoration.     

Effect of Temperature on Oxygen Consumption of the Leopard Shark, Triakis Semifasciata

The leopard shark, Triakis semifasciata, regularly resides in California's Tomales Bay, which is characterized by thermally different regions ranging from 10°C to 26°C during the summer. Past studies have shown that leopard sharks feed on benthic invertebrate prey similar to that of the sympatric bat ray, Myliobatis californica. Fishes' metabolic (oxygen consumption) rates typically increase with temperature increases, and we measured leopard sharks' metabolic responses and sensitivity to ambient temperature, using flow-through respirometry. Leopard shark oxygen consumption rate increased with increasing temperature, over a range of 12–24°C, with a typical temperature sensitivity (Q₁₀ = 2.51). Whereas bat rays use a highly temperature-sensitive metabolism to efficiently feed (in warmer waters) and digest (in cooler waters) during different phases of the diel cycle, leopard sharks possess a more typical metabolic temperature sensitivity that allows for high-tide foraging, throughout the diel cycle.     

农业景观中山体的植物多样性分布：地形和土地利用的综合影响

 农业景观中,山体是被广阔农田包围的生境岛屿,是生物多样性保护的重点地段。存在人类干扰时,决定山体植物多样性的主要因素不是面积、年龄和隔离程度,而是地形和土地利用。在这种情况下,从岛屿生物地理学的观点来理解生物多样性的分布规律是不合适的,因此本文采用直接对比分析方法对此进行说明。选择环渤海地区河北省遵化市（39°55′～40°22′ N, 117°34′～118°14′ E）境内的10个山体,从山顶到山底沿坡面设置样带。记录不同坡位的土地利用类型及宽度,分层调查各个土地利用类型的乔木层、灌木层和草本层物种丰     

大亚湾水域原甲藻调查与鉴定

对1998年至2000年在广东省大亚湾海域所采集的样品进行了观察和分析。发现有8种原甲藻(Prorocentrum);反曲原甲藻（Prorocentrum sigmoides),海洋原甲藻（P.micans)。三角棘原甲藻（P.triestinum)。具齿原甲藻（P.mexicanum)和原甲藻未知种（P.sp)。对它们的形态特征和生态分布进行了描述。     

Heavy Metals in Seagrasses and Algae of Pos'et Bay, Sea of Japan

The contents of heavy metals in Sargassum algae and seagrasses from Pos'et Bay in the Sea of Japan were studied. The concentrations of Fe, Mn, Cu, Zn, and Cr in the algae and seagrass leaves were correlated with each other. The concentrations of heavy metals in brown algae and seagrasses from Pos'et Bay were largely close to background levels. Increased contents of some metals found in macrophytes in the area of the port of Pos'et were due to local environmental pollution; around Furugel'm Island, to periodical upwelling and drift currents from the mouth of the Tumannaya River; and, at Cape Deger, to the cyclonic current.     

Toxic activity from cultures of Karlodinium micrum (=Gyrodinium galatheanum) (Dinophyceae)—a dinoflagellate associated with fish mortalities in an estuarine aquaculture facility

The goal of this study was to test for, and partially characterize, toxic activity associated with the dinoflagellate Karlodinium micrum. Since 1996, three fish kill events associated with blooms of K. micrum have occurred at HyRock Fish Farm, an estuarine pond aquaculture facility raising hybrid striped bass on the Chesapeake Bay, MD, USA. Using an assay based on the lysis of rainbow trout erythrocytes, cultures of a Chesapeake Bay isolate of K. micrum have been shown to produce toxic substances which are released upon cell disturbance or damage. The LC₅₀ for hemolysis of a sonicated cell suspension was 2.4×10⁴ cells ml⁻¹, well within the range of cell concentrations observed associated with fish kills. The toxic activity from K. micrum cells and culture filtrates was traced to two distinct fractions that co-elute with polar lipids. The LC₅₀ for hemolysis of the larger of these two fractions (Tox A) was 284 ng ml⁻¹ while the LC₅₀ of the second, smaller, fraction (Tox B) was 600 ng ml⁻¹. For comparison, the LC₅₀ for the standard hemolysin saponin was 3203 ng ml⁻¹. At concentrations of 800 and 2000 ng ml⁻¹, respectively, Tox A was further shown to be ichthyotoxic to zebrafish (Danio rerio) larvae (80% mortality), and cytotoxic to a mammalian GH(4)C(1) cell line (100% LDH release). At a concentration of 600 ng ml⁻¹ Tox B was shown to be cytotoxic to a mammalian GH(4)C(1) cell line (>30% LDH release), but not ichthyotoxic to zebrafish (D. rerio) larvae up to a concentration of 250 ng ml⁻¹. Although treatment with either algicidal copper or potassium permanganate caused significant lysis of K. micrum cells (>70%), toxic activity was released after treatment with copper and eliminated following treatment with potassium permanganate. This observation in cultures is consistent with observations made at HyRock Fish Farm where significantly higher mortality was observed following treatment of a K. micrum bloom with copper sulfate compared to treatment with potassium permanganate. This study represents the first direct evidence of the toxicity of K. micrum isolated from the Chesapeake Bay.     

Features of Temporal Differentiation of the Chum Salmon Oncorhynchus ketaof the Anadyr Bay Region at Different Abundance Levels

The temporal heterogeneity of chum salmon stock of the Anadyr Bay region was investigated on the basis of a set of discrete external morphological features and fluctuating asymmetry level of some meristic structures. Differentiation of Anadyr Bay chum salmon during the spawning run was found to be associated with the abundance level of spawning stock in a particular year. Sharply pronounced temporal heterogeneity, based on the investigated characteristics, in the area near the river mouth can be considered as an indicator of the subsequent deficiency of spawners on the spawning grounds of rivers in the Anadyr Bay region.     

SUMMER DIVING BEHAVIOR OF MALE WALRUSES IN BRISTOL BAY, ALASKA

Pacific walruses ( Odobenus rosmarus divergens ) make trips from ice or land haul-out sites to forage for benthic prey. We describe dive and trip characteristics from time-depth-recorder data collected over a one-month period during summer from four male Pacific walruses in Bristol Bay, Alaska. Dives were classified into four types. Shallow (4 m), short (2.7 min), square-shaped dives accounted for 11% of trip time, and many were probably associated with traveling. Shallow (2 m) and very short (0.5 min) dives composed only 1% of trip time. Deep (41 m), long (7.2 min), square-shaped dives accounted for 46% of trip time and were undoubtedly associated with benthic foraging. V-shaped dives ranged widely in depth, were of moderate duration (4.7 min), and composed 3% of trip time. These dives may have been associated with navigation or exploration of the seafloor for potential prey habitat. Surface intervals between dives were similar among dive types, and generally lasted 1–2 min. Total foraging time was strongly correlated with trip duration and there was no apparent diel pattern of diving in any dive type among animals. We found no correlation between dive duration and postdive surface interval within dive types, suggesting that diving occurred within aerobic dive limits. Trip duration varied considerably within and among walruses (0.3–9.4 d), and there was evidence that some of the very short trips were unrelated to foraging. Overall, walruses were in the water for 76.6% of the time, of which 60.3% was spent diving.     

Mercury contamination and stable isotopes reveal variability in foraging ecology of generalist California gulls

Environmental contaminants are a concern for animal health, but contaminant exposure can also be used as a tracer of foraging ecology. In particular, mercury (Hg) concentrations are highly variable among aquatic and terrestrial food webs as a result of habitat- and site-specific biogeochemical processes that produce the bioaccumulative form, methylmercury (MeHg). We used stable isotopes and total Hg (THg) concentrations of a generalist consumer, the California gull (Larus californicus), to examine foraging ecology and illustrate the utility of using Hg contamination as an ecological tracer under certain conditions. We identified four main foraging clusters of gulls during pre-breeding and breeding, using a traditional approach based on light stable isotopes. The foraging cluster with the highest δ¹⁵N and δ³⁴S values in gulls (cluster 4) had mean blood THg concentrations 614% (pre-breeding) and 250% (breeding) higher than gulls with the lowest isotope values (cluster 1). Using a traditional approach of stable-isotope mixing models, we showed that breeding birds with a higher proportion of garbage in their diet (cluster 2: 63–82% garbage) corresponded to lower THg concentrations and lower δ¹⁵N and δ³⁴S values. In contrast, gull clusters with higher THg concentrations, which were more enriched in ¹⁵N and ³⁴S isotopes, consumed a higher proportion of more natural, estuarine prey. δ³⁴S values, which change markedly across the terrestrial to marine habitat gradient, were positively correlated with blood THg concentrations in gulls. The linkage we observed between stable isotopes and THg concentrations suggests that Hg contamination can be used as an additional tool for understanding animal foraging across coastal habitat gradients.