温度和光照强度对海藻场瓦氏马尾藻碎屑分解的影响

通过气候培养箱在室内模拟不同光照强度及温度条件,测定海藻场瓦氏马尾藻碎屑(简称海藻碎屑)分解速率变化及海藻碎屑对海藻场海域无机营养盐贡献度,旨在为探究大型海藻碎屑的生态服务效能提供科学依据。结果表明:海藻碎屑剩余物质干重和分解速率受温度影响不显著(P0.05),而光照强度影响显著(P0.05);不同温度、光强条件下,海藻碎屑质量损失率在2个月的实验周期内皆大于60%,且温度25.15℃、光强3200 lx条件更有利于海藻碎屑分解;温度对海藻碎屑分解释放氮磷营养盐影响不显著(P0.05);在同一温度(25.15℃)条件下,有无光照条件对水体铵态氮、硝态氮和亚硝态氮营养盐浓度变化影响不显著(P0.05),但对正磷酸盐浓度影响显著(P0.05);光照强度对水体内铵态氮和正磷酸盐浓度变化具有显著影响(P0.05),对硝态氮和亚硝态氮浓度变化影响不显著(P0.05);根据海藻场瓦氏马尾藻碎屑量估算出对现场海域水体溶解无机氮累积贡献量为4.597~17.321 mg·L~(-1),溶解无机磷累积贡献27.989~76.304 mg·L~(-1)。研究表明,不同温度条件下,瓦氏马尾藻碎屑分解释放铵态氮和正磷酸盐的量大于硝态氮和亚硝态氮,温度越高越利于铵态氮释放,而正磷酸盐则更利于在低温下分解释放;随光照强度的升高,氮磷营养盐释放趋势相反,正磷酸盐释放量随光照强度增大而受到抑制。     

生长光强对六个橡胶树品种幼苗光合特性的影响

研究了6个橡胶树品种幼苗(适应1年后)在不同生长光强(100%、50%、25%和5%自然光)下的叶片光合系统对光强和CO2浓度的响应特性。结果表明,6个橡胶树品种对不同的光环境均表现出较强的适应性。在不同生长光强下,橡胶树幼苗叶片的最大光合速率(Pmax)、光补偿点(LCP)、暗呼吸速率(Rd)、磷酸丙糖利用速率(TPU)、最大羧化速率(Vcmax)和最大电子传递速率(Jmax)以及叶绿素含量(Chl)均有显著差异(P<0.05),而光饱和点(LSP)和AQY(表观量子效率)则无显著差异。相同生长光强下,6个橡胶树品种间叶片的最大光合速率(Pmax)、暗呼吸速率(Rd)、磷酸丙糖利用速率(TPU)、最大电子传递速率(Jmax)和叶绿素含量(Chl)有显著差异(P<0.05),其光补偿点(LCP)、最大羧化速率(Vcmax)和表观量子效率(AQY)则无显著差异。综合比较各参数,RRIM600、云研77-4和PR107适宜于相对光强为100%~50%的植胶环境,而云研77-2、GT1和热研523适宜于相对光强为50%~25%的植胶环境。     

海头红的海水铁含量适宜性

20℃条件下,研究了6个不同海水铁含量处理[23(自然海水,对照)、100、300、500、700、900μg·L-1]对海头红(Plocamium telfairiae)相对生长速率、藻胆蛋白含量及过氧化物酶和固氮酶活力的影响,分析了海头红的海水铁含量适宜性。结果表明:经30 d培育实验,海水铁含量为100μg·L-1处理组海头红的相对生长速率(RGR)达到最大值(1.14%·d-1),极显著高于其他海水铁含量处理组(P0.01),而海水铁含量为300~900μg·L-1处理组海头红的RGR在0.26~0.34%·d-1,与对照组无明显不同(P0.05);海头红3种藻胆蛋白含量均随海水铁含量的增加呈先增加后缓慢下降的变化趋势,并于100μg·L-1时达到最大值,海头红过氧化物酶活力亦在海水铁含量100μg·L-1条件下达到最高值(14.5U·mg-1),显著高于其他处理组(P0.05),但不同海水铁含量对海头红固氮酶活力无显著影响(P0.05)。适宜性分析表明,在设定的5个海水富铁处理中,100μg·L-1铁含量对海头红的促生长作用最显著。     

遮光条件下不同种源土沉香幼苗的光合特性与生长速率分析

以3个来源于广东茂名的土沉香[ Aquilaria sinensis (Lour.) Spreng.]种源(大白、小白和大黄)和1个来源于云南的土沉香种源的1年生幼苗为研究对象,对不同遮光条件下[相对光强100％(对照,自然光强)、50％、25％和5％]4个种源幼苗叶片的净光合速率(Pn)的光响应和CO2响应曲线、光合和气体交换参数、叶绿素含量和叶绿素a/b( Chla/b)值进行了分析,并比较了4个种源幼苗的相对生长速率(RGR).结果表明:4个种源的Pn均随光合光量子通量密度的增加而上升,且对照组各种源的Pn值均明显高于各处理组;4个种源的Pn值均随胞间CO2浓度的升高或相对光强的增大逐渐提高.随相对光强的降低,4个种源的最大光合速率、光补偿点、光饱和点、暗呼吸速率、最大电子传递速率、最大羧化速率和磷酸丙糖利用速率均下降或显著下降(P＜0.05),而表观量子效率则略有升高.在相对光强100％ ～ 25％条件下,随相对光强降低,4个种源的叶绿素含量显著提高、Chla/b值显著减小;大白和小白种源的RGR逐渐增大,大黄种源的RGR差异不显著,而云南种源的RGR显著减小.而在相对光强5％条件下,大黄和云南种源的叶绿素含量显著降低,Chla/b值显著增大,RGR显著减小;大白和小白种源幼苗全部死亡.由种源间的比较可见:4个种源的各项光合参数以及叶绿素含量、相对生长速率均有一定的差异,其中云南种源的各项指标总体上均最低.综合来看,土沉香为半阳生植物,对不同的光环境表现出相对较强的适应性.     

光环境对胡桃楸幼苗生长与光合作用的影响

为了解胡桃楸幼苗对光的需求及适应规律,采用Li-6400便携式光合测定系统研究了不同光环境处理（100%、60%、30％和15%自然光）条件下3年生胡桃楸幼苗（适应1年后）叶片光合能力的季节变化及其对光强的响应.结果表明：在春季,胡桃楸幼苗对光反应不敏感,夏季和秋季随着光强的增加,叶片的最大光合速率、最大羧化速率和最大电子传递速率均显著增加（P<0.05）.光饱和点随光强的下降而降低（P<0.05）,表观量子效率、暗呼吸速率和光补偿点在不同光环境下未发现显著差异.100%和60%自然光处理的幼苗相对生长率差异不显著,但是随着光强下降,相对生长率显著下降（P<0.05）,为60%>30％>15%自然光处理.胡桃楸幼苗对不同的光环境表现出较强的适应性和可塑性;同时,通过降低光饱和点和减少碳积累,也能适应15%～30％自然光环境.     

光照和氮营养对水曲柳苗木光合特性的影响

采用室内沙培方式,设计不同光强(2水平)和N浓度(4水平)处理,探讨1年生水曲柳幼苗叶片光合速率和荧光参数对环境变化的生理响应.结果表明:与全光照相比,遮光处理使苗木叶片最大光合速率(Amax)、光补偿点(LCP)以及光化学猝灭系数(qP)明显下降,但使表观量子效率(AQY)、最大荧光(Fm)和最大光化学效率(Fv/Fm)明显增加.同时,苗木叶片单位面积的叶绿素a、类胡萝卜素、总叶绿素含量以及叶绿素a/b在遮光条件下较低.2种光强下的Fm、Fv/Fm、ψpsⅡ和qP均随着供N浓度的增加而显著增加(P＜0.05),其中ψpsⅡ在低N时增加较快而高N时较慢,甚至略有下降.光强和N浓度在水曲柳苗木叶片Fm、ψpsⅡ、Fv/Fm、qN以及qP上均具有显著的交互作用(P＜0.05).     

光强和硝态氮水平对铜藻(Sargassum horneri)生长和光合生理特性的影响

以金潮种铜藻(Sargassum horneri)为对象,探讨了不同硝态氮水平下光照强度对其生长和光合生理特性的影响,以期为金潮暴发机制的研究提供一定的参考。实验设置了高(100μmol·L-1)、低(自然海水,50μmol·L-1) 2个硝态氮浓度和高(150μmol photons·m-2·s-1)、中(60μmol photons·m-2·s-1)、低(10μmol photons·m-2·s-1)三个光照水平,检测了藻体在不同硝态氮浓度和光照条件下适应培养7 d后生长、色素含量、可溶性糖含量、可溶性蛋白含量、氮吸收速率及最大光合放氧速率(Pmax)等生理指标的变化。结果表明:氮浓度相同时,铜藻的生长速率、可溶性糖含量、可溶性蛋白含量、氮吸收速率、Pmax均随光照强度的增加而增加,而色素含量随着光照强度的增加而降低;低氮条件下,除类胡萝卜素外,以上指标在高光处理下均显著高于低光处理(P0.05);高氮条件下,除可溶性糖外,以上指标在高光条件下也均显著高于低光处理(P0.05);同一光照强度下,色素及可溶性蛋白含量、氮吸收速率及Pmax随氮浓度的增加而增加;可溶性糖含量随着硝态氮浓度的增加而减少;且在3个光照条件下,高氮处理下藻体的Pmax均显著高于低氮处理。总之,不同光照和氮浓度处理7 d后,高光、高氮适应后的藻体表现出较高的生长和光合作用潜能。铜藻断裂后漂浮于海面极易获得较高光强条件,而富营养海水中的高氮条件会刺激铜藻的光合潜能而使其加速生长,进而加剧铜藻金潮的暴发。     

闽江河口湿地土壤CH4产生与氧化速率对外源氮、硫添加的响应

通过室内培养实验,研究了外源氮、硫添加对闽江河口湿地土壤CH_4产生/氧化速率以及土壤理化性质的短期影响。NH_4Cl(N1)和NH_4NO_3(N3)处理在各培养阶段均显著促进土壤CH_4产生速率(P0.05),较对照分别提高136.70%和136.55%;NH_4Cl+K_2SO_4(NS1)和NH_4NO_3+K_2SO_4(NS3)处理在培养第3、6、12、15和18天均显著促进了CH_4产生速率(P0.05)。KNO_3(N2)、K_2SO_4(S)处理在不同培养时间对CH_4产生速率影响均不显著(P0.05);KNO_3+K_2SO_4(NS2)处理除在第21天外(P0.05),其他时间影响均不显著(P0.05)。N2、N3、NS2和NS3处理均显著促进了土壤CH_4氧化速率(P0.05),平均CH4氧化速率较CK分别提高了145.30%、142.93%、139.48%和112.68%。整体而言,不同添加处理并没有显著改变湿地土壤CH_4产生/氧化速率的时间变化规律,各处理均表现为随培养时间先增加而后逐渐降低。短期培养结束后,土壤可溶性有机碳(DOC)、电导率、p H值在不同处理间均不存在显著差异(P0.05);土壤NH+4-N含量在N1、N3、NS1和NS3处理下,NO_3~--N含量在N2、N3、NS2和NS3处理下,SO_4~(2-)含量在S、NS1、NS2和NS3处理下均显著高于对照处理(P0.05)。相关分析显示,DOC、铵态氮(NH+4-N)和硝态氮(NO_3~--N)是氮、硫添加处理下影响闽江河口湿地土壤CH_4产生/氧化速率短期变化的主要控制因素。     

不同氮、磷配比人工海水对海带胚孢子早期发育的影响

利用不同氮、磷配比的人工海水培养海带胚孢子,观察其对海带早期发育的影响.结果表明：培养于人工海水中的海带胚孢子80%能够正常发育,但与培养于天然海水中的对照组仍存在显著差异,且人工海水中海带胚孢子的萌发和配子体的形成时间滞后,人工海水培养所形成的海带雌配子体数量显著高于雄配子体（P<0.001）;不同氮、磷配比的人工海水对海带胚孢子萌发率的影响不同,N∶P＞15∶1的氮磷比会降低海带胚孢子的萌发率,而缺乏氮或磷营养盐的人工海水则极显著抑制海带胚孢子的萌发（P<0.001）;海带胚孢子能够在人工海水中进行早期发育,但人工海水中的氮、磷营养盐浓度以及氮/磷比均会对海带发育初期胚孢子的萌发率产生影响;人工海水中氮、磷营养盐的缺乏会导致海带配子体形成时间的滞后,并对其雌雄分化产生一定影响.     

海带养殖在桑沟湾多营养层次综合养殖系统中的生态功能

采用现场和实验生态学方法研究了大型经济海藻——海带(Saccharina japonica)的生长、光合作用和氮营养盐的吸收特性。实验结果表明:在1个生长周期内(约200d),海带的湿重与养殖天数呈明显的幂函数(W=1.3886 t~(1.362),R~2=0.9611),海带湿重是长度的幂函数(W=0.0071 L~(2.0882),R~2=0.9392);海带的光合作用放氧速率(O_2mg/h)与湿重(g)具有明显的线性相关(R~2范围为0.950—0.981),直线斜率(反应单位时间单位重量光合作用放氧速率)的变化范围为0.096—0.195(平均0.191),养殖初期单位鲜重的光合放氧能力较弱,后期趋于稳定;不同部位海带藻片对TIN的吸收速率不同,中带部上部(60—110cm)和基部(20—50cm)的吸收速率大于中带部下部(150—200cm)和边缘部,氮饥饿后最初0.5—1h对TIN的吸收速率最高(0.6μmol/g WW),培养24h可去除介质中TIN(初始浓度24.2μmol/L,密度4g/L)的64.2%—97.1%,10℃条件下藻片对营养盐的吸收率和去除率均大于4℃。海带藻片对NO_3-N的吸收速率大于对NH_4-N的吸收速率,24h后对NO_3-N的收速率趋于稳定。结果显示,海带具有较高的生长速度、光合作用产氧和营养盐吸收能力。海带养殖后期,每天可以增加氧气28.8g/m2(光周期按14h计算),收获时海带的平均碳氮含量分别为33.1%和1.8%,以桑沟湾海带养殖产量8.45万t计算,每年可移除2.8万t碳和1538t氮,海带在多营养层次综合养殖系统中具有较高的生态功能。     

Do Cues Matter? Highly Inductive Settlement Cues Don't Ensure High Post-Settlement Survival in Sea Urchin Aquaculture

Increasing settlement and post-settlement survival during the critical transition from planktonic larvae to benthic juveniles will increase efficiency for sea urchin aquaculture. This study investigated the effects of temperature and settlement cues on the settlement and post-settlement survival of the sea urchin Tripneustes gratilla during this phase. The current commercial methodology, which utilises natural biofilm settlement plates, was tested and resulted in low settlement (<2%) and poor post-settlement survival (<1% of settled urchins). In laboratory trials, settlement was high and unaffected by temperatures between 24 and 30°C, but significantly decreased at 33°C. Development of spines, however, was significantly affected by temperatures over 29°C. Mirroring this result, post-settlement survival was optimal between 24-28°C. In laboratory assays, the macroalgae Sargassum linearifolium and Corallina officinalis, and seawater conditioned with these algae, induced significantly higher settlement (>90%) than a natural biofilm (～25%). The addition of macroalgae-conditioned seawater to natural biofilm significantly increased settlement rates (>85%). Mixed consortia and single strains of bacteria isolated from macroalgae, biofilms and adult conspecifics all induced significant settlement, but at significantly lower rates than macroalgae. No evidence was found that higher rates of settlement to bacteria on macroalgae were generated by a cofactor from the macroalgae. Age of bacterial cultures, culturing bacteria on solid and liquid media and concentration of nutrients in cultures had little effect on settlement rates. Finally, macroalgae-conditioned seawater combined with natural biofilm settlement plates induced significantly higher settlement than to the biofilm plates alone in a commercial scale trial. However, high post-settlement mortality resulted in equivalent survival between treatments after 25 days. This study highlights that settlement studies should extend to post-settlement survival, which remains poor for T. gratilla and is a significant obstacle to increasing efficiency for aquaculture.     

Quantitative and qualitative analyses of dissolved organic matter released from Ecklonia cava Kjellman, in Oura Bay, Shimoda, Izu Peninsula, Japan

Release of dissolved organic matter (DOM) was studied on macroalga, Ecklonia cava Kjellman, by in situ field bag experiments, which were designed to keep the algal body under natural field condition, in Oura Bay, Shimoda, Izu Peninsula, Japan, from August 2003 to May 2005. The experiments were conducted 6 times in different seasons. The concentrations of dissolved organic carbon (DOC) in the experimental bag generally increased during the first 1-2 days, showing the release of DOC from algae. The daily release rates of DOC varied between 0.12 and 5.8 mgC per g (dry wt) of the algal blades per day. The seasonal variability of the DOC release rate was similar to those of the growth and the photosynthetic rates reported by the previous studies on E. cava in the same location. The fractions of the DOC release of the net primary production accounted for 18-62%. These contributions are comparable to other macroalgae in the previous studies (27-43%) using other macroalgae. Analysis of organic composition of DOM using gas chromatography (neutral aldose composition) and spectrometry (UV-visible and fluorescence) indicates that E. cava usually release extracellular products containing mucilaginous polysaccharides containing fucose as a main constituent and colored dissolved organic matter (CDOM). The release of these organic compounds is likely performed as the ordinary metabolism of brown algae. An exceptional release of a considerable amount of protein and carbohydrates mainly composed of mannose was found in June 2004, probably reflecting leakage of the intracellular material by an autolysis of the algal cells. The high DOM release rate in the present study suggests that macroalgae would be one of the important DOM producers in coastal regions.     

Effects of Antarctic sea ice biota on seeding as studied in aquarium experiments

Summary The potential seeding impact of sea ice microbial communities was studied during late austral winter early spring 1988 in the Weddell Sea, Antarctica. Experiments were performed in seawater aquariums with natural seawater and seawater enriched with crushed ice. Algal, protozoan and bacterial cell numbers were followed, as well as nutrients and DOC levels. The results showed a potential seeding effect of sea ice communities to the water column. However, the type of ice communities differed greatly from each other and the effect of such seeding will be patchy. In our experiments seeding of seawater by ice rich in algae, flagellates and/or particulate organic carbon lead to the development of communities dominated either by diatoms or bacteria.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

MACROALGAL TISSUE NUTRIENTS AS INDICATORS OF NITROGEN AND PHOSPHORUS STATUS IN THE FLORIDA KEYS

This study used the tremendous biochemical and ecological diversity of macroalgae to assess nitrogen and phosphorus availability at a broad, ecosystem‐level scale in the Florida Keys and nearby waters. Spatial variation in tissue nutrients (carbon, C; nitrogen, N; phosphorus, P) of dominant macroalgae were assessed, both as ratios and absolute values, along 12 inshore‐offshore transects in the Florida Keys and at 10 stations in nearby Florida Bay. The resulting detailed analysis demonstrated spatial and temporal patterns in macroalgal tissue nutrients. The transect data revealed no universal inshore‐offshore patterns in tissue nutrients and no obvious “hotspots” of nutrient enrichment. Similarly, when data were compared among segments, there was no universal geographical pattern in tissue nutrients for all species. The most striking result was that the N and P status of macroalgae in Florida Bay was significantly different than other locations. Macroalgae collected from Florida Bay generally had higher N and lower P levels than algae collected elsewhere. The most common inshore‐offshore pattern was higher %N and lower %P availability inshore; however, limited inshore‐offshore differences in N:P ratio suggests that both nutrients were generally readily available in proportional amounts required by the various species. Most species in this study had higher %N, and to a lesser extent, higher %P and %C in March than in July. Based on the published literature on other species of macroalgae, it appears that N and P are generally available in sufficient quantities that most macroalgal growth is not limited by either nutrient.     

Effect of melting Antarctic sea ice on the fate of microbial communities studied in microcosms

Although algal growth in the iron-deficient Southern Ocean surface waters is generally low, there is considerable evidence that winter sea ice contains high amounts of iron and organic matter leading to ice-edge blooms during austral spring. We used field observations and ship-based microcosm experiments to study the effect of the seeding by sea ice microorganisms, and the fertilization by organic matter and iron on the planktonic community at the onset of spring/summer in the Weddell Sea. Pack ice was a major source of autotrophs resulting in a ninefold to 27-fold increase in the sea ice-fertilized seawater microcosm compared to the ice-free seawater microcosm. However, heterotrophs were released in lower numbers (only a 2- to 6-fold increase). Pack ice was also an important source of dissolved organic matter for the planktonic community. Small algae (<10 μm) and bacteria released from melting sea ice were able to thrive in seawater. Field observations show that the supply of iron from melting sea ice had occurred well before our arrival onsite, and the supply of iron to the microcosms was therefore low. We finally ran a “sequential melting” experiment to monitor the release of ice constituents in seawater. Brine drainage occurred first and was associated with the release of dissolved elements (salts, dissolved organic carbon and dissolved iron). Particulate organic carbon and particulate iron were released with low-salinity waters at a later stage.     

Effect of light intensity on algal biomass accumulation and biodiesel production for mixotrophic strains Chlorella kessleri and Chlorella protothecoide cultivated in highly concentrated municipal wastewater

In this research, the effect of light intensity on biomass accumulation, wastewater nutrient removal through algae cultivation, and biodiesel productivity was investigated with algae species Chlorella kessleri and Chlorella protothecoide. The light intensities studied were 0, 15, 30, 60, 120, and 200 μmol m(-2) s(-1). The results showed that light intensity had profound impact on tested responses for both strains, and the dependence of these responses on light intensity varied with different algae strains. For C. kessleri, the optimum light intensity was 120 μmol m(-2) S(-1) for all responses except for COD removal. For C. protothecoide, the optimum light intensity was 30 μmol m(-2) S(-1). The major components of the biodiesel produced from algae biomass were 16-C and 18-C FAME, and the highest biodiesel contents were 24.19% and 19.48% of dried biomass for C. kessleri and C. protothecoide, respectively. Both species were capable of wastewater nutrients removal under all lighting conditions with high removal efficiencies.     

Dopamine release by Ulvaria obscura (Chlorophyta): environmental triggers and impacts on photosynthesis,growth, and survival of the releaser

In the NE Pacific, Ulvaria obscura is a common component of “green tide” blooms. It is also the only alga known to produce dopamine, which is released into seawater on sunny days when Ulvaria is emersed and then rehydrated. To better understand the mechanisms associated with dopamine release, we experimentally determined whether light quantity and quality, desiccation, temperature, exudates from conspecifics, and dissolved dopamine caused dopamine release. We also examined the effects of desiccation on Ulvaria's ability to photosynthesize, grow, and survive. Desiccation was the only factor that caused significant amounts of dopamine to be lost from U. obscura tissues. The loss of water from Ulvaria tissues was strongly and positively correlated with the loss of dopamine after rehydration. Only 56% of desiccated algae survived for 1 week, compared to 100% of undesiccated control algae. Desiccated algae lost 77% of their pigmented surface area and grew only 15% as much as undesiccated algae, which remained fully pigmented. The oxygen saturation of water containing Ulvaria that was desiccated and then rehydrated was significantly lower than that of seawater containing undesiccated algae. Thus, desiccation, which is coupled with dopamine release, is associated with the deterioration and death of some, but not all, tissues in Ulvaria. Although dopamine released into seawater can reduce the survival or growth of potential competitors, its release is associated with significant physiological stress and tissue mortality. However, the survival and continued growth of some Ulvaria tissues indicates that a net fitness benefit to release dopamine following desiccation cannot be ruled out.     

Marine macroalgae affect abundance and community richness of bacterioplankton in close proximity1

Many macroalgae employ chemical means to suppress epibiosis by micro‐ and macroorganisms. Previous studies have focused on the effects of tissue extracts of entire algae on a few bacterial isolates, thereby missing not only ecologically relevant bacteria but also natural delivery mechanisms of algal antimicrobial agents. In this study, we investigated the potential antimicrobial effects of waterborne macroalgal metabolites utilizing a culture‐independent approach to compare the bacterial community richness in seawater in the presence and absence of macroalgae. The methodology comprised the collection of planktonic bacteria in algal culture water on membrane filters followed by filter PCR and denaturant gradient gel electrophoresis (DGGE) of 16S rRNA gene sequences of harvested bacteria with universal primers. Similarity analysis distinguished two groups of macroalgae under investigation, one of which showed >55% difference, and the other <50% difference in bacterial community composition in comparison to natural seawater. The bacterial abundance in algal culture water of different algae was reduced between 20% and 50%. Further experiments demonstrated that the observed effects were caused by waterborne algal compounds. However, some bacterial types were exclusively eliminated in the presence of algae, indicating causative modes of action other than direct exposure of bacteria to waterborne compounds, such as surface‐mediated antimicrobial effects.     

ANNUAL PRODUCTIVITY AND EXTRACELLULAR RELEASE OF DISSOLVED ORGANIC COMPOUNDS BY THE EPIBENTHIC ALGAL COMMUNITY OF A BRACKISH MARSH1

Annual productivity and excretion of organic compounds by epibenthic algae in a coastal Texas marsh were investigated using ¹⁴C techniques. Over the course of two years, productivity and extracellular release were measured bimonthly to assess the environmental factors affecting seasonal patterns. Annual productivity was estimated to be 71 gc·m^?2, approximately 10% of the estimated net aerial productivity of the grass canopy in this area. The percentage of photoassimilated carbon released was fairly constant, and the rate of excretion appeared to be primarily dependent upon the rate of carbon fixation. Greater rates of release were observed with high salinity, low soil moisture conditions. It was estimated that up to 10% of the DOC in adjacent tidal creek water could be produced by this community and could represent an important source of nutrients for consumers in the system.     

烟台养马岛潮间带大型海藻分布特征及环境影响因素

2010年4月—2011年3月对烟台养马岛潮间带大型海藻进行了逐月调查.在养马岛潮间带共设置了A、B两个点,对大型海藻物种组成、生物量以及与环境变化的关系进行了研究.结果表明: 调查区域共有大型海藻35种,其中红藻24种,占总数的68.6%;绿藻6种,占总数的17.1%;褐藻5种,占总数的14.3%.夏季优势种以褐藻和绿藻为主,秋、冬、春季优势种以红藻和褐藻为主,鼠尾藻在各季节中均为优势种.大型海藻生物量呈现夏季高、冬季低的特点,生物量最高值出现在6月,A、B采样点大型海藻生物量最小值分别出现在1月和11月,具有温带海域藻类变化特点.温度、营养盐和pH对大型海藻生物量有显著影响.