Zooplankton invasions: a brief review,plus two case studies from the northeast Pacific Ocean

Invasions of aquatic habitats by non-indigenous species (NIS), including zooplankton, are occurring at an alarming rate and are causing global concern. Although hundreds of such invasions have now been documented, surprisingly little is known about the basic biology and ecology of these invaders in their new habitats. Here we provide an overview of the published literature on NIS zooplankton, separated by life history (holoplankton vs. meroplankton), habitat (marine, estuarine, freshwater), and biological level of organization or topic (e.g. distribution and range extension, physiology, behavior, feeding, community impacts, ecosystem dynamics, etc). Amongst the many findings generated by our literature search, perhaps the most striking is the paucity of studies on community and ecosystem level impacts of NIS zooplankton, especially in marine and estuarine systems. We also present some results from two ongoing studies of invasive zooplankton in the northeast Pacific Ocean – Pseudodiaptomus inopinus in Washington and Oregon coastal estuaries, and Tortanus dextrilobatus in San Francisco Bay. Both of these Asian copepods have recently expanded their range and can at times be extremely abundant (10³ m^–3). We also examine some aspects of the trophic (predator–prey) ecology of these two invasive copepods, and find that they are likely to be important in the flow of material and energy in the systems in which they now pervade, although their impacts at the ecosystem level remain to be quantified. Finally, the findings of both our literature search and our two case studies of invasive zooplankton lead us to make several recommendations for future research.     

Genetic diversity in wild populations of Paulownia fortunei

The genetic diversities of 16 Paulownia fortunei populations involving 143 individuals collected from 6 provinces in China were analyzed using amplified fragment length polymorphism (AFLP). A total of 9 primer pairs with 1169 polymorphic loci were screened out, and each pair possessed 132 bands on average. The percentage of polymorphic bands (98.57%), the effective number of alleles (1.2138–1.2726), Nei’s genetic diversity (0.1566–0.1887), and Shannon’s information index (0.2692–0.3117) indicated a plentiful genetic diversity and different among Paulownia fortune populations. The genetic differentiation coefficient between populations was 0.2386, while the gene flow was 1.0954, and the low gene exchange promoted genetic differentiation. Analysis of variance indicated that genetic variation mainly occurred within populations (81.62% of total variation) rather than among populations (18.38%). The 16 populations were divided by unweighted pair-group method with arithmetic means (UPGMA) into 4 groups with obvious regionalism, in which the populations with close geographical locations (latitude) were clustered together.     

Genetic variability and population structure of sockeye salmon from the Asian Coast of Pacific Ocean

Variability of six microsatellite loci and 45 single nucleotide polymorphism (SNP) loci was analyzed in 17 samples of sockeye salmon from 10 major spawning watersheds on the Asian coast of the Pacific Ocean. On the basis of the analysis of SNP loci variability of sockeye salmon in the examined part of the range, five population groups were identified, including local stocks from the Palana, Okhota, and Kamchatka rivers, as well as the population groups of Southwestern Kamchatka, and Northeastern Kamchatka and Chukotka. Rather different pattern of samples differentiation was obtained by estimating variability of six microsatellite DNA loci. Regional complexes of the eastern and western coasts of Kamchatka were identified. Moreover, sockeye salmon from the Palana River fell into the cluster of Western Kamchatka populations, while the population from the Okhota River and Meynypilgin lake–river system (Chukotka), confined to the subperiphery of the range, where the most differentiated from the others. The possible reasons for the discrepancies and high divergence of the Palana River and the Okhota River sockeye salmon populations, inferred from the SNP markers analysis, are discussed.     

Genetic stock identification of overwintering chum salmon in the North Pacific Ocean

Understanding stock and age-specific seasonal migrations of Pacific salmon during ocean residence is essential to both the conservation and management of this important resource. Based upon 11 microsatellites assayed on 265 individuals collected aboard international research surveys during winter 2009, we found substantial differences in the age-specific origin of chum salmon (Oncorhynchus keta) in the North Pacific Ocean. Overall, Asian stocks dominated the collections, however, ocean age 1 fish were primarily of Japanese origin and ocean age 2–3+ fish were predominantly of Russian origin. These results suggest that cohorts of chum salmon stocks migrate nonrandomly in the North Pacific Ocean and adjacent seas.     

Late Holocene sea level indicators from twelve atolls in the central and eastern Tuamotus (Pacific Ocean)

New sea-level data for the late Holocene period are reported from twelve atolls of the Tuamotu archipelago: Faaite, Hikueru, Marokau, Hao, Amanu, Tatakoto, Pukarua, Nukutavake, Vairaatea, Tureia, Nukutipipi, and Hereheretue. The data come from coral conglomerate outcrops, coral colonies in growth position, in situ reef framework and marine notches; they give consistent results, and their ages are controlled by 29 radiocarbon datings. The Holocene MSL remained 0.8±0.2 m higher than at present, from before 4000 years BP until at least 1500 years BP, then dropped gradually to the present level. This pattern is very similar to that reported from the northwest Tuamotus, suggesting the absence of measurable differential vertical movements over a distance greater than 1300 km during the late Holocene. Effects of the 1983 cyclones on reef morphology are reported from some atolls and radiocarbon dates of some storm-generated reef blocks are given.     

Genetic effects of harvest on wild animal populations

Human harvest of animals in the wild occurs in terrestrial and aquatic habitats throughout the world and is often intense. Harvest has the potential to cause three types of genetic change: alteration of population subdivision, loss of genetic variation, and selective genetic changes. To sustain the productivity of harvested populations, it is crucial to incorporate genetic considerations into management. Nevertheless, it is not necessary to disentangle genetic and environmental causes of phenotypic changes to develop management plans for individual species. We recommend recognizing that some genetic change due to harvest is inevitable. Management plans should be developed by applying basic genetic principles combined with molecular genetic monitoring to minimize harmful genetic change.     

Population Genetic Structure of Pacific Herring Clupea pallasii in the Northwestern Pacific Ocean Based on Microsatellite Analysis

Journal of Ichthyology - The population genetic structure of Pacific herring Clupea pallasii in the northwestern Pacific Ocean is studied based on the polymorphism analysis of 11 microsatellite...     

Genetic structure of korean wild populations of the Medaka Oryzias latipes inferred from allozymic variation

Previous allozymic studies have revealed that Korean wild populations of Oryzias latipes have differentiated regionally, and are composed of two distinct groups, the East Korean Population and the China-West Korean Population. Recently, mitochondrial DNA (mtDNA) sequencing and restriction fragment length polymorphism (RFLP) analyses have confirmed these two groups, and shown that the distribution ranges of the two groups overlap in western Korea. In order to describe the detailed distributions of the two groups and the gene flow between them, genotypes of 13 allozymic loci were determined in 444 specimens from 96 localities in Korea. The two major groups were supported by remarkable allele frequency differences at six diagnostic loci: ACP*, AMY*, CK-A*, LDH-A*, PGM* and TF*. Individuals with the typical "eastern" genotype were mainly distributed in eastern and southern areas. In contrast, fish with the "western" genotype were predominant in the western area, and were further divided into two subgroups (the Han River and Geum River Subpopulations) by unique alleles at the ADH* locus. In the western coast, two distinct (eastern and western) genotypes were distributed in a mosaic fashion. This distribution pattern was identical to those from mtDNA analyses. Although the distribution patterns of the alleles at three loci (GPI-A*, LDH-C* and SOD*) showed introgressive conditions between the two groups, each population was nearly fixed as either the eastern or western genotype at all six diagnostic loci despite the proximity among samples. Therefore, it is suggested that some reproductive isolation mechanisms exist between the two groups in natural habitats.     

Genetic variation in central and peripheral populations of Excoecaria agallocha from Indo-West Pacific

Genetic diversity and differentiation were studied in Excoecaria agallocha L., a mangrove species growing on the coastlines of the Indo-West Pacific region. Twenty natural populations of E. agallocha were sampled from the Malay Peninsula (central population), and in Southern China, North Australia, Sri Lanka and Southern Japan (peripheral populations). Our results showed that central populations from Malay Peninsula possessed significantly higher genetic diversity than the peripheral ones (P < 0.05). Analysis of molecular variation (AMOVA) revealed that genetic variability was partitioned at 22.9% among regions, 23.6% among populations within regions, and 53.5% within populations. Genetic differentiation (G_ST = 0.300) among the six central populations was stronger than those from peripheral regions. Populations from North Australia clustered closely together in the dendrogram and were distinct from the rest of the populations. Those from Southern Japan, Southern China and Sri Lanka also clustered closely together, respectively. However, populations from Malay Peninsula did not cluster by region. The east coast populations of Malay Peninsula (including Pasir population) were more genetically similar to the populations from Southern China than those from the west coastline of Malay Peninsula. Our study suggests that ocean currents, land barriers, limited dispersal ability of seeds, and founder effect may play important roles in the distribution of genetic diversity in E. agallocha.     

Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal

The mesopelagic zone of the northeast Pacific Ocean is an important foraging habitat for many predators, yet few studies have addressed the factors driving basin-scale predator distributions or inter-annual variability in foraging and breeding success. Understanding these processes is critical to reveal how conditions at sea cascade to population-level effects. To begin addressing these challenging questions, we collected diving, tracking, foraging success, and natality data for 297 adult female northern elephant seal migrations from 2004 to 2010. During the longer post-molting migration, individual energy gain rates were significant predictors of pregnancy. At sea, seals focused their foraging effort along a narrow band corresponding to the boundary between the sub-arctic and sub-tropical gyres. In contrast to shallow-diving predators, elephant seals target the gyre-gyre boundary throughout the year rather than follow the southward winter migration of surface features, such as the Transition Zone Chlorophyll Front. We also assessed the impact of added transit costs by studying seals at a colony near the southern extent of the species' range, 1,150 km to the south. A much larger proportion of seals foraged locally, implying plasticity in foraging strategies and possibly prey type. While these findings are derived from a single species, the results may provide insight to the foraging patterns of many other meso-pelagic predators in the northeast Pacific Ocean.     

Comparing radiolarian and diatom diversity and abundance from the northeast Pacific

Particle trap samples (VERTEX) from 4 locations in the northeast Pacific were used to compare centric and pennate diatoms with nassellarian and spumellarian radiolarians. The proportion of pennates and nassellarians were highest at VERTEX 3 from the northeast tropical oceans, off the west coast of Mexico. Colonial radiolarians were characteristic of warm, high saline waters from the southern edge of the north Pacific central gyre, north of Hawaii (VERTEX 4), while pennate diatoms were abundant. The subtropic oceanic Pacific (VERTEX 5A) had more pennate diatoms, while VERTEX (5C), in a coastal cyclonic eddy located west of California, had an even proportion of centric and pennate diatoms. Comparison of major faunas and flora at various oceanic sites of present siliceous sedimentation in conjunction with atmospheric, hydrographic and chemical data, can be helpful in reconstructing paleoceanographic and paleoenvironmental conditions of the past oceans throughout the Phanerozoic.     

斑节对虾两个野生亲虾种群遗传多样性

采用RAPD和mtDNA 16S rRNA基因序列分析方法对海南和马来西亚斑节对虾(Penaeus monodon)种群进行了遗传多样性和遗传分化研究.结果表明:15个RAPD随机引物共检测到82个位点,海南和马来西亚种群的多态位点比例分别为75.90％和76.83％,杂合度分别为0.199和0.218,遗传多样性指数分别为0.276和0.288,种群间的遗传距离为0.015;16S rRNA基因检测的种内遗传变异较低,马来西亚和海南种群的核苷酸多样性分别为0.011和0,种群之间的遗传距离为0.008;马来西亚种群比海南种群的遗传变异水平要高得多,且海南种群可能起源于马来西亚种群;进行遗传选育时可考虑引进马来西亚亲虾作为奠基群体.     

Gelatinous and soft-bodied zooplankton in the Northeast Pacific Ocean: Phosphorus content and potential resilience to phosphorus limitation

Hydrobiologia - Marine ecosystems on continental shelves face multiple challenges due to anthropogenic disturbances, many of which can change the seawater stoichiometry (C:N:P) and consequently...     

Export of dissolved iron from river catchments in northeast Japan

Landscape and Ecological Engineering - This study investigated the export of dissolved iron (DFe) from river catchments with emphasis on land use and land cover (LULC). The DFe concentrations were...     

Geographical variations in the jack mackerel Trachurus symmetricus murphyi populations in the southeastern Pacific Ocean as evidenced from the associated parasite communities

The composition of the metazoan parasite communities within 2 fishing zones along the Chilean coast were compared to determine the population structure of the jack mackerel Trachurus symmetricus murphyi (Nichols) in these 2 geographical locations. More than 7,780 parasites belonging to 15 taxa were collected between 1990 and 1996 in 71 samples comprised of 3,946 hosts. The same taxa were found in both fishing zones. However, jack mackerel from northern Chile had a higher abundance of cymothoid isopods, Ceratothoa spp., whereas those from southern Chile had more Rhadinorhynchus trachuri, Hysterothylacium sp. larvae, and Anisakis type I larvae. Results were similar at all community levels because all parasites had low prevalence and infracommunities had low total abundance and richness. Analyses at the component community level may be more adequate for stock identification when infracommunities are simple. There were significant differences in composition of parasite communities between years in each fishing zone, presumably as a result of the increase in offshore catches since 1994. These results reinforce the hypothesis that more than 1 ecological stock of the jack mackerel exists in the southeastern Pacific and contradict the current assumption of a single stock in the management of this heavily exploited fish species.     

Genetic structure of wild bean populations in their South-Andean centre of origin

 The genetic structure of wild common bean populations was studied in the South-Andean centre of origin of the species. Plants were collected from 21 populations in Argentina and genetic variability was assessed for molecular and resistance markers. Polymorphism was weak for phaseolin, the major seed-storage protein, and for RAPD markers, while a high level of polymorphism was observed for resistance to anthracnose, one of the most important diseases of common bean. For the three traits, within-population variability was important and represented between 43.6% and 67.5% of the total variation. Although among-population differentiation was significant for all the traits, no correlation was found between the population distances calculated from RAPDs and resistance. These results indicate that pathogen selection pressure may be an important factor influencing the distribution of variability within and among host plant populations. Received: 28 October 1997 / Accepted: 25 November 1997     

Variation in Hypericins from wild populations ofHypericum perforatum L. in the Pacific Northwest of the U.S.A.

Representatives from eight wild populations ofHypericum perforatum L. were collected from Montana and Northern California at flowering, and subsequently analyzed for hypericin and pseudohypericin using HPLC analysis. Total individual plant concentrations in these wild populations were from 0.0003–0.1250% dry weight (DW) hypericin and 0.0019–0.8458% DW pseudohypericin. In general, hypericin concentrations were highest in the plant’s reproductive (flower and bud) tissues, followed by leaf and stem tissues, respectively. Hypericin and pseudohypericin concentrations were positively correlated in all samples, although the relative ratio of hypericin to pseudohypericin varied with site location.