两种大型底栖动物生物扰动对沉积物颗粒垂直分布的影响

以直径0.4~0.5 mm玻璃珠作为示踪颗粒,探讨了多毛类的丝鳃虫Cirratulus chrysoderma和双壳类的菲律宾蛤仔Ruditapes philippinarum 2种大型底栖动物生物扰动作用对沉积物颗粒垂直分布的影响,为评价大型底栖动物对沉积环境的影响以及探讨海洋"碳汇"等作用提供基础资料。生物扰动的测定装置由长28 cm、直径10.5 cm的PVC管制成,下端用塑料膜密封。实验海水盐度30、温度20℃。菲律宾蛤仔分3种规格:大(壳长32.64 mm±0.08 mm,湿重7.34 g±0.45 g)、中(25.30 mm±0.11 mm,3.54 g±0.19 g)、小(20.34 mm±0.06 mm,1.63 g±0.13 g)。丝鳃虫体长80.00 mm±15.00 mm、湿重1.40 g±0.20 g,设3个密度:255、510、1 020只/m2。分别在扰动实验开始后的第7天和第20天取样。2种大型底栖动物属于不同生物扰动功能组;第7天丝鳃虫密度与示踪颗粒迁移率正相关,第20天则呈负相关关系;示踪颗粒的迁移率与菲律宾蛤仔的规格呈负相关关系。扰动时间与示踪颗粒进入沉积物的绝对量和到达的最大深度均呈正相关关系,而与其迁移率呈负相关。     

Buried in the sand: Uncovering the ecological roles and importance of rays

Rays (superorder Batoidea) are the most diverse group of elasmobranchs, and many are threatened with extinction. However, there remain areas where research on the ecology of this group is lacking, from trophic interactions to their importance to ecosystem structure and function. Such ecological insights are critical for predicting the potential consequences of changes in their population sizes. Our aim was to synthesize the existing ray ecology literature and identify key knowledge gaps in order to provide a framework for future research. Numerous studies describe ray diets, and the number of studies using biochemical methods to address ray trophic interactions is increasing. The implications of ray predator–prey interactions on population dynamics of prey and how ray foraging might influence ecosystem dynamics through bioturbation remain relatively unexplored, despite claims that rays are ecologically important because they are bioturbators and because of their potential to deplete stocks of commercially important bivalves. Therefore, to better integrate rays in our understanding of marine community dynamics, there is a need to: (i) combine behavioural data with dietary information to describe predator–prey interactions; (ii) understand how ray bioturbation affects biogeochemical cycles and infaunal communities; (iii) elucidate conditions under which rays might initiate or transmit trophic cascades through consumptive and non‐consumptive pathways; and (iv) consider anthropogenic influences on the ecological roles and importance of rays.     

Responses of scallop biodeposits to bioturbation by a deposit‐feeder Apostichopus japonicus (Echinodermata: Holothuroidea): does the holothurian density matter?

The deposit‐feeding holothurians can reduce the negative impact of bivalve farming by feeding and reworking bivalve wastes (biodeposits) in the context of co‐culture. To test effects of the bioturbation by holothurians of different densities on bivalve wastes, a stocking density regime of the sea cucumber Apostichopus japonicus (35.4 ± 1.2 g, mean ± SE) was set at 0.0, 6.6, 13.2 ind m^?2, and responses of the biotic parameters including chlorophyll a concentration (Chl. a), bacterial biomass and the abiotic ones as oxidation‐reduction potential (ORP), organic matter (OM), organic carbon (OC), total nitrogen (TN) and organic phosphorus (OP) in biodeposits discharged by Japanese scallop Patinopecten yessoensis were investigated. Results showed that A. japonicus grew in a density‐dependent manner, and the density‐dependent effect on both biotic and abiotic parameters in biodeposits were also observed. Apostichopus japonicus stimulated a transfer process from reduction to weak reduction state of the biodeposits with a trend of higher density holothurians stimulating the process more. Furthermore, A. japonicus significantly controlled the bacterial abundance and Chl. a, as well as reducing the contents of OM, OC, TN and OP in the biodeposits. Yet, the response of abiotic parameters delayed rather than that of biotic parameters, underling the biotic parameters could be more sensitive to bioturbation than the abiotic ones. Our study suggests that the bioturbation of A. japonicus plays an important role in retarding organic waste accumulation and cleansing nutrients in bivalve farming wastes under co‐culture condition and the bioremediation capacity may be closely dependent on its stocking density in practice.     

水丝蚓对稻田土壤微生物的影响

通过野外采样和室内控制试验,初步研究了底栖动物水丝蚓对稻田土壤微生物(区系、生物量、生理群)的影响.结果表明,水丝蚓组稻田土壤细菌、放线菌、真菌数量均高于对照组,分别达到极显著、显著、极显著.水丝蚓组稻田土壤微生物生物量碳(BC)和生物量氮(BN)高于对照组,均达到极显著差异水平.水丝蚓促进了稻田土壤硫化细菌、硝化细菌、纤维素分解菌、氨化细菌和固氮菌的增殖,抑制了反硫化细菌和反硝化细菌的生长和活性,有利于增加土壤硫、氮、磷等生源要素的有效性,提高稻田土壤养分的利用效率.利用底栖动物的生物扰动效应,根据农业系统中不同营养级生物的生态特性,可开发多级物质循环、多层次利用、多物种共生的现代农业技术,为可持续农业提供支持.     

霍甫水丝蚓（Limnodrilus hoffmeisteri）扰动对表层沉积物细菌群落结构和多样性的影响

为研究大型底栖动物霍甫水丝蚓（Limnodrilus hoffmeisteri）对表层沉积物中细菌群落结构和多样性的影响,设计了沉积物-水微宇宙的实验,模拟太湖梅梁湾霍甫水丝蚓（Limnodrilus hoffmeisteri）的自然分布特征,运用末端限制性片段长度多态性技术（T-RFLP）比较了有无霍甫水丝蚓（Limnodrilus hoffmeisteri）分布的沉积物样品中细菌群落的动态变化。结果表明,水丝蚓组和对照组沉积物细菌群落结构相似性无显著差异（P〉0.05）,可见太湖梅梁湾目前的水丝蚓生物量引起的生物扰动对表层沉积物细菌群落结构影响不明显;实验中后期只在处理组中出现的206 bp以及处理组含量高于对照组的370 bp T-RFs都可能是Nitrosomonas属的氨氧化细菌,提示大型底栖动物霍甫水丝蚓的存在可能为氨氧化细菌提供了适合的生态位。     

不同盐度下凡纳滨对虾扰动作用对沉积物-水界面营养盐通量的影响

采用室内培养方法,研究了三个盐度水平下(盐度分别为5‰,20‰,35‰)凡纳滨对虾的扰动作用对沉积物-水界面NH+4-N、NO-3-N、NO-2-N和SRP通量的影响。结果显示:凡纳滨对虾在三个盐度下都可以促进沉积物NH+4-N的释放,但是促进效果不相同,总体表现为盐度越高促进作用越明显;盐度为5‰时对虾对沉积物NO-3-N释放的促进作用最低,但对NO-2-N释放的促进作用最高;盐度为20‰时对虾对沉积物NO-3-N和NO-2-N释放的促进作用均较高,且对沉积物NO-3-N释放的促进作用是三个盐度水平下最高的。实验的前8d各盐度下对虾对SRP的促进效果没有显著差异,而实验持续到15d后高盐度组对虾的促进作用比低盐度组显著。     

缢蛏扰动及排氨作用对上覆水氮营养盐含量和通量的影响

底栖生物的扰动及排泄等生命活动会影响沉积物-水界面营养盐含量与迁移状况。采用室内模拟培养缢蛏的方法,在23℃、盐度22、pH=8的环境条件下,设置低、中、高密度3组以及对照组,进行为期25 d的室内模拟实验,每隔5天采集上覆水进行氮营养盐组分含量和通量的测定,探讨缢蛏扰动及其排氨作用对上覆水中氮营养盐的影响。结果表明,缢蛏扰动促进了上覆水中氨氮(NH₄⁺)、硝态氮(NO₃^-+NO₂^-)含量的增加,随着缢蛏投放密度的增加,NH₄⁺含量呈现明显的增大趋势,而NO₃^-+NO₂^-含量先增加后降低。NH₄⁺通量为-0.195~0.273 mmol/(m²·d),即沉积物中的氨氮向上覆水中释放,NO₃^-+NO₂^-通量为-0.554~0.038 mmol/(m²·d),表明沉积物从上覆水中吸收硝态氮。考虑到缢蛏代谢排氨的影响,用排氨数据校核氨氮含量,尽管NH₄⁺含量有小幅降低,但随时间的变化趋势不变。另外NH₄⁺通量在实验初期变化较大,从沉积物向上覆水释放转变为上覆水中NH₄⁺向沉积物迁移,随后趋于平稳,变化不明显。因此,缢蛏的扰动促进了沉积物与上覆水之间氮营养盐的交换,其中排氨作用在实验前期对通量的影响较大,随时间的推移排氨作用的影响逐渐降低。     

Visualization of the respiring bacteria in sediments inhabited by Capitella sp. 1

ABSTRACT:    We used the tetrazolium salt 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride (INT) to locate sites of active (respiring) bacterial populations in sediments inhabited by the deposit-feeding polychaete Capitella sp. 1. In sediment microcosms, this organism created typical protruding tubes on the sediment surface and burrows from day 1. Within a couple of hours after adding INT into the overlying water, the red color of the reduced form of INT (INT-formazan) became apparent in the water column and on the sediment surface. During the following 24 h, part of the subsurface burrows turned red and the color of formazan intensified with time during incubation. Spatial heterogeneity of the distribution of the formazan deposits along burrows also was recognized. Microscopic observations revealed that the tubes and feces produced by Capitella sp. 1, as well as detrital particles, were the sites of intensive formazan deposition. Observation with higher magnification (up to ×1250) revealed that INT-formazan was present either as bacterial intercellular deposits or as microgranules covering entire bacterial cells. In situ application of INT into a sediment microcosm provides a simple and sensitive way to visualize the impact of burrow structures created by small macrobenthos, such as Capitella , on the distribution of metabolically active bacteria.