Prediction of mesophotic coral distributions in the Au‘au Channel, Hawaii

The primary objective of this study was to predict the distribution of mesophotic hard corals in the Au‘au Channel in the Main Hawaiian Islands (MHI). Mesophotic hard corals are light-dependent corals adapted to the low light conditions at approximately 30 to 150 m in depth. Several physical factors potentially influence their spatial distribution, including aragonite saturation, alkalinity, pH, currents, water temperature, hard substrate availability and the availability of light at depth. Mesophotic corals and mesophotic coral ecosystems (MCEs) have increasingly been the subject of scientific study because they are being threatened by a growing number of anthropogenic stressors. They are the focus of this spatial modeling effort because the Hawaiian Islands Humpback Whale National Marine Sanctuary (HIHWNMS) is exploring the expansion of its scope—beyond the protection of the North Pacific Humpback Whale (Megaptera novaeangliae)—to include the conservation and management of these ecosystem components. The present study helps to address this need by examining the distribution of mesophotic corals in the Au‘au Channel region. This area is located between the islands of Maui, Lanai, Molokai and Kahoolawe, and includes parts of the Kealaikahiki, Alalākeiki and Kalohi Channels. It is unique, not only in terms of its geology, but also in terms of its physical oceanography and local weather patterns. Several physical conditions make it an ideal place for mesophotic hard corals, including consistently good water quality and clarity because it is flushed by tidal currents semi-diurnally; it has low amounts of rainfall and sediment run-off from the nearby land; and it is largely protected from seasonally strong wind and wave energy. Combined, these oceanographic and weather conditions create patches of comparatively warm, calm, clear waters that remain relatively stable through time. Freely available Maximum Entropy modeling software (MaxEnt 3.3.3e) was used to create four separate maps of predicted habitat suitability for: (1) all mesophotic hard corals combined, (2) Leptoseris, (3) Montipora and (4) Porites genera. MaxEnt works by analyzing the distribution of environmental variables where species are present, so it can find other areas that meet all of the same environmental constraints. Several steps (Figure 0.1) were required to produce and validate four ensemble predictive models (i.e., models with 10 replicates each). Approximately 2,000 georeferenced records containing information about mesophotic coral occurrence and 34 environmental predictors describing the seafloor’s depth, vertical structure, available light, surface temperature, currents and distance from shoreline at three spatial scales were used to train MaxEnt. Fifty percent of the 1,989 records were randomly chosen and set aside to assess each model replicate’s performance using Receiver Operating Characteristic (ROC), Area Under the Curve (AUC) values. An additional 1,646 records were also randomly chosen and set aside to independently assess the predictive accuracy of the four ensemble models. Suitability thresholds for these models (denoting where corals were predicted to be present/absent) were chosen by finding where the maximum number of correctly predicted presence and absence records intersected on each ROC curve. Permutation importance and jackknife analysis were used to quantify the contribution of each environmental variable to the four ensemble models.

Ecological Condition of Coastal Ocean Waters within Stellwagen Bank National Marine Sanctuary: 2008

In June 2008, the NOAA National Ocean Service (NOS), in conjunction with the EPA National Health and Environmental Effects Laboratory (NHEERL), conducted an assessment of the status of ecological condition of soft-bottom habitat and overlying waters within the boundaries of Stellwagen Bank National Marine Sanctuary (SBNMS). The sanctuary lies approximately 20 nautical miles east of Boston, MA in the southwest Gulf of Maine between Cape Ann and Cape Cod and encompassing 638 square nautical miles (2,181 km2). A total of 30 stations were targeted for sampling using standard methods and indicators applied in prior NOAA coastal studies and EPA’s Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA). A key feature adopted from these studies was the incorporation of a random probabilistic sampling design. Such a design provides a basis for making unbiased statistical estimates of the spatial extent of ecological condition relative to various measured indicators and corresponding thresholds of concern. Indicators included multiple measures of water quality, sediment quality, and biological condition (benthic fauna, fish tissue contaminant levels). Depths ranged from 31 – 137 m throughout the study area. About 76 % of the area had sediments composed of sands (< 20 % silt-clay), 17 % of the area was composed of intermediate muddy sands (20 – 80 % silt-clay), and 7 % of the sampled area consisted of mud (> 80 % siltclay). About 70 % of the area (represented by 21 sites) had sediment total organic carbon (TOC) concentrations < 5 mg/g and all but one site (located in Stellwagen Basin) had levels of TOC < 20 mg/g, which is well below the range potentially harmful to benthic fauna (> 50 mg/g). Surface salinities ranged from 30.6 – 31.5 psu, with the majority of the study region (approximately 80 % of the area) having surface salinities between 30.8 and 31.4 psu. Bottom salinities varied between 32.1 and 32.5 psu, with bottom salinities at all sites having values above the range of surface salinities. Surface-water temperatures varied between 12.1 and 16.8 ºC, while near-bottom waters ranged in temperature from 4.4 – 6.2 ºC. An index of density stratification (Δσt) indicated that the waters of SBNMS were stratified at the time of sampling. Values of Δσt at 29 of the 30 sites sampled in this study (96.7 % of the study area) varied from 2.1 – 3.2, which is within the range considered to be indicative of strong vertical stratification (Δσt > 2) and typical of the western Gulf of Maine in summer. Levels of dissolved oxygen (DO) were confined to a fairly narrow range in surface (8.8 – 10.4 mg/L) and bottom (8.5 – 9.6 mg/L) waters throughout the survey area. These levels are within the range considered indicative of good water quality (> 5 mg/L) with respect to DO. None of these waters had DO at low levels (< 2 mg/L) potentially harmful to benthic fauna and fish.

Cruise report: regional assessment of ecosystem condition and stressor impacts along the northwestern Gulf of Mexico Shelf. NOAA Ship 'Nancy Foster' NF-11-07-RACOW (August 8-16, 2011)

This cruise report is a summary of a field survey conducted along a portion of the U.S. continental shelf in northwestern Gulf of Mexico (GOM), at navigable depths along the coastline seaward to the shelf break (~100m) from about 89°30' W to 95°28' W longitude, August 8 – 16, 2011 on NOAA Ship Nancy Foster Cruise NF-11-07-RACOW. Synoptic sampling of multiple ecological indicators was conducted at each of 34 stations throughout these waters using a random probabilistic sampling design. The original study design consisted of 50 stations extending from the Mississippi delta all the way to the U.S./Mexican border, but vessel failures precluded sampling at 16 stations within the western-most portion of the study area. At each station samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants in sediments and target demersal biota; sediment toxicity; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as salinity, temperature, dissolved oxygen, turbidity, pH, sediment grain size, and organic carbon content. Other indicators, from a human-dimension perspective, were also recorded, including presence of vessels, oil rigs, surface trash, visual oil sheens in sediments or water, marine mammals, or noxious/oily sediment odors. The overall purpose of the survey was to collect data to assess the status of ecosystem condition and potential stressor impacts throughout the region, based on these various indicators and corresponding management thresholds, and to provide this information as a baseline for determining how such conditions may be changing with time. While sample analysis is still ongoing, some preliminary results and observations are reported here. A final report will be completed once all data have been processed.

Seascape ecology of coastal biogenic habitats: advances, gaps, and challenges

We review the progress made in the emerging field of coastal seascape ecology, i.e. the application of landscape ecology concepts and techniques to the coastal marine environment. Since the early 1990s, the landscape ecology approach has been applied in several coastal subtidal and intertidal biogenic habitats across a range of spatial scales. Emerging evidence indicates that animals in these seascapes respond to the structure of patches and patch mosaics in different ways and at different spatial scales, yet we still know very little about the ecological significance of these relationships and the consequences of change in seascape patterning for ecosystem functioning and overall biodiversity. Ecological interactions that occur within patches and among different types of patches (or seascapes) are likely to be critically important in maintaining primary and secondary production, trophic transfer, biodiversity, coastal protection, and supporting a wealth of ecosystem goods and services. We review faunal responses to patch and seascape structure, including effects of fragmentation on 5 focal habitats: seagrass meadows, salt marshes, coral reefs, mangrove forests, and oyster reefs. Extrapolating and generalizing spatial relationships between ecological patterns and processes across scales remains a significant challenge, and we show that there are major gaps in our understanding of these relationships. Filling these gaps will be crucial for managing and responding to an inevitably changing coastal environment. We show that critical ecological thresholds exist in the structural patterning of biogenic ecosystems that, when exceeded, cause abrupt shifts in the distribution and abundance of organisms. A better understanding of faunal–seascape relationships, including the identifications of threshold effects, is urgently needed to support the development of more effective and holistic management actions in restoration, site prioritization, and forecasting the impacts of environmental change.

Cruise report: regional assessment of ecosystem condition and stressor impacts along the northeastern Gulf of Mexico shelf; NOAA Ship Nancy Foster NF-10-09-RACOW (August 13-21, 2010)

This cruise report is a summary of a field survey conducted along the continental shelf of the northeastern Gulf of Mexico (GOM), encompassing 70,062 square kilometers of productive marine habitats located between the Mississippi Delta and Tampa Bay, August 13–21, 2010 on NOAA Ship Nancy Foster Cruise NF-10-09-RACOW. Synoptic sampling of multiple ecological indicators was conducted at each of 50 stations throughout these waters using a random probabilistic sampling design. At each station samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants (metals, pesticides, TPHs, PAHs, PCBs, PBDEs) in sediments and target demersal biota; sediment toxicity; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as depth, salinity, temperature, dissolved oxygen, turbidity, pH, CDOM fluorescence, sediment grain size, and organic carbon content. Discrete water samples were collected just below the sea surface, in addition to any deeper subsurface depths where there was an occurrence of suspicious CDOM fluorescence signals, and analyzed for total BTEX/TPH and carcinogenic PAHs using immunoassay test kits. Other indicators of potential value from a human-dimension perspective were also recorded, including presence of any vessels, oil rigs, surface trash, visual oil sheens in sediments or water, marine mammals, or noxious/oily sediment odors. The overall purpose of the survey was to collect data to assess the status of ecosystem condition and potential stressor impacts throughout the region, based on these various indicators and corresponding management thresholds, and to provide this information as a baseline for determining how such conditions may be changing with time. In addition to the original project goals, both the scientific scope and general location of this project are relevant to addressing potential ecological impacts of the Deepwater Horizon oil spill. While sample analysis is still ongoing, a few preliminary results and observations are reported here. A final report will be completed once all data have been processed.

Cruise report: summer 2009 Sapelo Island National Estuarine Research Reserve ecological characterization (June 7 - June 13, 2009)

This cruise report is a summary of a field survey conducted within the Sapelo Island National Estuarine Research Reserve (SINERR), located on the Georgia coastline, June 7 – June 13, 2009. Multiple indicators of ecological condition and human dimensions were sampled synoptically at each of 30 stations throughout SINERR using a random probabilistic sampling design. Samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants (metals, pesticides, PAHs, PCBs, PBDEs) in sediments and target demersal biota; nutrient and chlorophyll levels in the water column; bacterial contaminants in the water column; and other basic habitat characteristics such as depth, salinity, temperature, dissolved oxygen, turbidity, total suspended solids, pH, sediment grain size, and organic carbon content. In addition to the fish samples that were collected for analysis of chemical contaminants relative to human-health consumption limits, other human-dimension indicators were sampled as well including presence or absence of fishing gear, vessels, surface trash, and noxious sediment odors. The overall purpose of the survey was to collect data to assess the status of ecosystem condition and potential stressor impacts throughout SINERR, based on these various indicators and corresponding management thresholds, and to provide this information as a baseline for determining how such conditions may be changing with time. While sample analysis is still ongoing a few preliminary results and observations are reported here. A final report will be completed once all data have been processed. The results will provide a comprehensive weight-of-evidence basis for evaluating current condition (aka a “state-of-the-SINEER environmental report”) and serve as a quantitative benchmark for tracking any future changes due to either natural or human disturbances. Another goal of the study is to demonstrate its utility as a possible model for assessing the status of condition at other NEERS sites using similar and consistent methods to promote system-wide regional and national comparisons.

Ecological condition of coastal ocean waters along the U.S. Mid-Atlantic Bight: 2006

In May 2006, the NOAA National Ocean Service (NOS), in conjunction with the EPA National Health and Environmental Effects Laboratory (NHEERL), conducted an assessment of the status of ecological condition of soft-bottom habitat and overlying waters throughout the mid-Atlantic Bight (MAB) portion of the eastern U.S. continental shelf. The study area encompassed the region from Cape Cod, MA and Nantucket Shoals in the northeast to Cape Hatteras in the south, and was defined using a one nautical mile buffer of the shoreline extended seaward to the shelf break (~100-m depth contour). A total of 50 stations were targeted for sampling using standard methods and indicators applied in prior NOAA coastal studies and EPA’s Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA). A key feature adopted from these studies was the incorporation of a random probabilistic sampling design. Such a design provides a basis for making unbiased statistical estimates of the spatial extent of ecological condition relative to various measured indicators and corresponding thresholds of concern. Indicators included multiple measures of water quality, sediment quality, and biological condition (benthic fauna). Through coordination with the NOAA Fisheries Service/Northeast Fisheries Science Center (NFS/NEFSC), samples of summer flounder (Paralichthys dentatus) also were obtained from 30 winter 2007 bottom-trawl survey stations in overlapping portions of the study area and used for analysis of chemical-contaminant body burdens.

Modeling the effect of striped bass (Morone saxatilis) on the population viability of Sacramento River winter-run chinook salmon (Onchorhynchus tshawytscha)

We estimated the impact of striped bass (Morone saxatilis) predation on winter-run chinook salmon (Oncorhynchus tshawytscha) with a Bayesian population dynamics model using striped bass and winter-run chinook salmon population abundance data. Winter-run chinook salmon extinction and recovery probabilities under different future striped bass abundance levels were estimated by simulating from the posterior distribution of model parameters. The model predicts that if the striped bass population declines to 512,000 adults as expected in the absence of stocking, winter-run chinook salmon will have about a 28% chance of quasi-extinction (defined as three consecutive spawning runs of fewer than 200 adults) within 50 years. If stocking stabilizes the striped bass population at 700,000 adults, the predicted quasi-extinction probability is 30%. A more ambitious stocking program that maintains a population of 3 million adult striped bass would increase the predicted quasi-extinction probability to 55%. Extinction probability, but not recovery probability, was fairly insensitive to assumptions about density dependence. We conclude that winter-run chinook salmon face a serious extinction risk without augmentation of the striped bass population and that substantial increases in striped bass abundance could significantly increase the threat to winter-run chi-nook salmon if not mitigated by increasing winter chinook salmon survival in some other way.

Assessment of some physico-chemical parameters of River Ogun (Abeokuta, Ogun State, southwestern Nigeria) in comparison with national and international standards

This study assessed the physico-chemical quality of River Ogun, Abeokuta, Ogun state, Southwestern Nigeria. Four locations were chosen spatially along the water course to reflect a consideration of all possible human activities that are capable of changing the quality of river water. The water samples were collected monthly for seven consecutive months (December 2011 – June 2012) at the four sampling stations. pH, air temperature (℃), water temperature (℃), conductivity (µs/cm) and total dissolved solids (mg/L) were conducted in-situ with the use of HANNA Combo pH and EC multi meter Hi 98129 and Mercury-in-glass thermometer while dissolved oxygen (mg/L), nitrate (mg/L), phosphate (mg/L), alkalinity (mg/L) and hardness (mg/L) were determined ex-situ using standard methods. Results showed that dissolved oxygen, hydrogen ion concentration, total hardness and nitrate were above the maximum permissible limit of National Administration for Food, Drugs and Control (NAFDAC), Standard Organization of Nigeria (SON), Federal Environmental Protection Agency (FEPA), United States Environmental Protection Agency (USEPA), European Union (EU) and World Health Organization (WHO) for drinking water during certain months of the study period. Results also showed that water temperature and conductivity were within the permissible limits of all the standards excluding FEPA. However, total dissolved solids and alkalinity were within the permissible limits of all the standards. Adejuwon and Adelakun, (2012) also reported similar findings on Rivers Lala, Yobo and Agodo in Ewekoro local government area of Ogun state, Nigeria. Since most of the parameters measured were above the maximum permissible limits of the national and international standards, it can be concluded that the water is unfit for domestic uses, drinking and aquacultural purposes and therefore needs to be treated if it is to be used at all. The low dissolved oxygen values for the first four months was too low i.e. < 5 mg/L. This is most likely as a result of the amount of effluents discharged into the river. To prevent mass extinction of aquatic organisms due to anoxic conditions, proper regulations should be implemented to reduce the organic load the river receives.

Review on hard coral recruitment (Cnidaria: Scleractinia) in Colombia

Recruitment, defined and measured as the incorporation of new individuals (i.e. coral juveniles) into a population, is a fundamental process for ecologists, evolutionists and conservationists due to its direct effect on population structure and function. Because most coral populations are self-feeding, a breakdown in recruitment would lead to local extinction. Recruitment indirectly affects both renewal and maintenance of existing and future coral communities, coral reef biodiversity (bottom-up effect) and therefore coral reef resilience. This process has been used as an indirect measure of individual reproductive success (fitness) and is the final stage of larval dispersal leading to population connectivity. As a result, recruitment has been proposed as an indicator of coral-reef health in marine protected areas, as well as a central aspect of the decision-making process concerning management and conservation. The creation of management plans to promote impact mitigation,rehabilitation and conservation of the Colombian coral reefs is a necessity that requires firstly, a review and integration of existing literature on scleractinian coral recruitment in Colombia and secondly, larger scale field studies. This motivated us to summarize and analyze all existing information on coral recruitment to determine the state of knowledge, isolate patterns, identify gaps, and suggest future lines of research.

横断山特有植物区系的物种多样性与生物地理学研究

前人对横断山区特有植物的宏生态学研究已有一定的资料积累，对横断山区在全球生物多样性保护中的关键地位和特有现象已有基本共识：（1）横断山区是全球生物多样性关键地区和生物多样性优先重点保护的热点地区之一；（2）横断山区不仅是中国的三大特有植物分布中心之一，而且是新特有中心和物种分化中心，特有现象的生态成因大于历史成因。横断山区种子植物种类丰富，且具有较高的特有现象，其中既有古特有成分也有新特有成分但更多的是新特有成分。但目前，关于横断山区特有现象与生态特征、特有种分布与物种丰富度、特有种丰富度与海拔梯度以及植被的关系等仍缺乏深入的研究。针对上述问题，本论文初步研究了横断山区（1）特有种的生活型、种子散布方式、传粉方式和繁育系统等生态特征，各生态特征之间的相关关系，以及它们的进化地位；（2）特有种的水平分布格局及环境成因；和（3）特有种和生态特征沿海拔梯度的变化规律。主要结论如下： 1．横断山区含特有植物2396个分类群（包括种、亚种和变种），隶属于372属90科。特有类群在372个属中的分布非常不均匀，约一半的特有类群（50.2%）集中分布在较少的属中（占总属数的6%），含特有类群的属大小差异很大，重要的大属是：马先蒿属、乌头属、杜鹃花属、翠雀属、紫堇属、虎耳草属、报春花属、小檗属、黄芪属、凤毛菊属、蚤缀属、橐吾属、龙胆属、景天属、柳属、苔草属、香茶菜属、凤仙花属、紫菀属、鼠尾草属和蝇子草属等，这些属多以横断山为分布和分化中心，为新特有成分。另外，地面芽植物和隐芽植物等占有绝对优势，而矮高位芽植物、高位芽植物、地面芽植物等占有较低的比例，反映了该特有区系的高山、亚高山植物区系特点，但又不乏与热带植物区系的渊源。与世界其它高山地区相比，该特有区系中的地面芽植物、隐芽植物和一年生植物有较高的比例。 2．草本、风力散布种子、昆虫传粉和两性花等为该特有植物区系的优势生态特征。除传粉方式和生活型间无明显的相互作用外，其它生态特征间都存在明显的正相关关系。定量化研究结果表明该特有区系特有种的传粉方式进化可塑性很小，处于保守（或原始）的进化地位。相反，种子散布方式和繁育系统的进化可塑性较大，处于衍生（或进化）的进化地位，是不同种系在历史发育过程中不同阶段的产物。生活型的进化地位在种间有较大的分异，具较小或较大可塑性的各占有一定的比例，因此生活型中既保留处于保守（或原始）的进化地位也有处于衍生（或进化）的进化地位，两种进化状态的生活型在该特有区系中并存，该特征不但是种系在进化早期决定的，同时也是不同种系在进化过程中获得的。 3． 特有种的分布不均匀，较高比例的特有种局限分布在较少的几个地区，北纬28-29°线是特有种丰富度重要的南北分界线。聚类分析结果表明其分布可以划分为3个物种聚集群：（1）北纬28-29°以北、北纬34°以南的藏东川西北物种聚集群；（2）北纬28-29°以南、北纬26°以北的藏东南—滇西北—川西南物种聚集群；和（3）北纬26°以南、北纬25°以北的滇西北物种聚集群。其中，藏东南—滇西北—川西南物种聚集群特有种丰富度最高，是横断山区特有种分布的核心区；滇西北物种聚集群特有种丰富度最低，藏东川西北物种聚集群特有种丰富度居中。藏东南—滇西北—川西南物种聚集群之所以特有种类丰富很有可能与该小区具有高的物种丰富度和落叶阔叶林、常绿/落叶针叶林的分布有密切的联系。在区域尺度上，横断山区总物种的分布中心与特有中心存在分异。尽管两者都处于北纬28-29°以南、北纬26°以北的藏东南—滇西北—川西南小区，但特有中心具有较小的分布范围，而总物种的丰富度中心分布范围较大。因此，我们推测特有分布中心不但与落叶阔叶林和常绿/落叶针叶林有密切的联系，而且也与物种丰富度有关。特有种与植被类型尤其是与常绿阔叶林和落叶阔叶林的关系研究对揭示特有现象的发生、性质和特点有一定的意义，有关研究尚需进一步开展。此外，海拔高差、区系物种丰富度、地理位置和单元面积为特有种丰富度地理分布的总体变异提供了74.7%的解释。 4．研究地区的南缘和东南缘有高比例的木本特有植物，而草本特有植物的比例相对最低，反映出该横断山区南缘的特有植物与热带植物区系的渊源关系，其成分多为一些古老的特有成分；而高比例和较高比例的草本特有植物在研究地区普遍存在，包括研究区域南、北的大部分地区，显然草本特有植物是横断山的优势特有成分。这种以草本特有植物为特征的高山、亚高山特有植物区系有别于我国其它两大特有植物分布中心。该特有中心的成因的最终解释还需要从物种形成（speciation）、灭绝（extinction）和扩散（biogeographic dispersal）——这三个直接影响一个地区物种数量变化的过程来考虑。 5．特有种丰富度沿海拔梯度呈“单峰” 变化曲线，在中海拔段达到峰值。与中国特有种、世界广布种相比，特有种的峰值最高，最适海拔分布范围最窄。特有率随海拔上升而逐渐增高，但在海拔5000-5500 m左右突然上升，在海拔6000 m左右达到最高值。说明（1）物种分布区和丰富度存在着正相关，即特有种具有小的分布区，而广布种的分布区较大；（2）特有率的线性变化规律反映了物种丰富度和特有现象之间的关系，即物种丰富度最大峰值以上海拔段物种数量减少，但特有率增加，说明了该特有区系的高海拔性质。 6．特有种沿海拔梯度表现出大小明显不同的物种聚集群，可能与横断山区的山地垂直气候及相应的植被类型有关。在2600-4600 m海拔段特有种数量最多，这可能与该海拔段分布着落叶阔叶林和常绿/落叶针叶林有密切的联系。特有植物沿海拔梯度可分为四个不同海拔段的物种聚集群：（1）200-1000 m；（2）1000-2600 m； （3）2600-4600 m；和（4）4600-6400 m。在对应海拔段依次分布着干热河谷稀树灌草丛、常绿阔叶林、落叶阔叶林和常绿/落叶针叶林、高山流石滩稀疏植丛。其中，分布在2600-4600 m海拔段的物种丰富度最高，1000-2600 m海拔段的物种丰富度次之，200-1000 m、4600-6400 m两个海拔段物种丰富度较低。 7．特有区系中占优势的生态特征包括草本、风力散布种子、虫媒传粉、两性花和克隆性等对海拔梯度的适应也呈“单峰” 变化曲线，但该主要特征与次要的生态特征（木本、动物散布种子、风媒传粉、单性花和非克隆性）相比，均具有较高的海拔峰值和较窄的最适分布范围，反映了主要生态特征对中、高海拔的适应特点。主要的生态特征与次要的生态特征并存构成了横断山区特有区系的基本生态特征。

High-speed wavelength conversion utilizing birefringence in semiconductor optical amplifiers

This paper describes a novel technique whereby a mixture of cross-phase and cross-gain modulation effects in an SOA causes polarization rotation of a cw probe beam in the presence of a signal pulse, enabling the transmission of the probe through a polarizer to be controlled. The benefits of this approach are: 1) Very high extinction ratios present in the wavelength converted signal (>30 achieved); 2) A non-inverted wavelength converted signal, which is advantageous for chirp-compensation;2 3) A simple and stable experimental set-up, 4) Converted pulses which can be shaped to be faster than the input pulses.

Ultrafast all-optical wavelength conversion using an integrated amplifier/DFB laser

Wavelength conversion in the 1550 nm regime was achieved in an integrated semiconductor optical amplifier (SOA)/DFB laser by modulating the output power of the laser with a light beam of a different wavelength externally injected into the SOA section. A 12 dB output extinction ratio was obtained for an average coupled input power of 75 μW with the laser section driven at 65 mA and the amplifier section at 180 mA. The response time achieved was as low as 13 ps with the laser biased at 175 mA even with low extinction ratios. The laser exhibits a similar recovery time allowing potentially very high bit-rate operation.

High speed wavelength conversion utilising an integrated amplifier/DFB laser

Wavelength conversion in the 1.55-μm regime was achieved for the first time in an integrated SOA/DFB laser by modulating the output power of the laser with a light beam of a different wavelength externally injected into the SOA section. In terms of speed, response times as low as 13ps were observed, though at the expense of reduced extinction ratio. Generally, these results indicate that operation in the 10s of GB/s should be possible.

Effects of pedestal suppression on gain-switched laser sources for 40 Gbit/s OTDM transmission

The performance of 40 Gbit/s optical time-division multiplexed (OTDM) communication systems can be severely limited when the extinction ratio of the optical pulses is low. This is a consequence of the coherent interference noise between individual OTDM channels. When taken alone, the multiple quantum well-distributed feedback laser+dispersion compensating fiber source exhibits a relatively poor extinction ratio which impairs its potential for use in a 40 Gbit/s OTDM system. However, with the addition of an electroabsorption modulator to suppress the pulse pedestals to better than 30 dB extinction, coherent interference noise is reduced, the bit-error-rate performance is greatly improved, and the source shows good potential for 40 Gbit/s OTDM communication.