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First mass stranding of Velella velella in New Zealand

DOI:10.1017/S175526720700872X
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Several million Velella velella per km were stranded on two west coast beaches from the end of October to the beginning of November 2006, and high numbers along the entire west coast of New Zealand. A few Velella strand most years, but this appears to be the first mass stranding ever recorded. The greatest length of 124 floats averaged 26 mm, and 72% were left sailors.
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JMBA2 - Biodiversity Records
Published on-line
First mass stranding of Velella velella in New Zealand
John E.C. Flux
Ecological Research Associates of New Zealand, 230 Hill Road, Belmont, Lower Hutt, New Zealand. E-mail: ux@paradise.net.nz
Several million Velella velella per km were stranded on two west coast beaches from the end of
October to the beginning of November 2006, and high numbers along the entire west coast of
New Zealand. A few Velella strand most years, but this appears to be the rst mass stranding ever
recorded. The greatest length of 124 oats averaged 26 mm, and 72% were left sailors.
INTRODUCTION
On 5 November 2006 along six km of rocky
beaches between Makara and Boom Rock (41°11'S
174°44'E ) enormous numbers of by-the-wind-
sailors (Velella velella) were dead and dying on the
tideline. There were a few pelagic barnacles with
them, but only ve Portugese-man-of-war (Physalia
utriculus), and no violet snails (Ianthina spp.). A
100x100 mm sample of the dried bodies layered 25
mm deep on the beach yielded 250 individuals, or
25,000 m–2. The tideline averaged about 1 m wide
(Figure 1), giving a total for the 6 km stretch of at
least 100 million Velella.
Two days later at Paraparaumu beach (40°54'S
174°59'E) live Velella were being washed ashore at
a density of about 1 m–1, but the dried bodies on
the tideline averaged about 100 m–1, assessed over
50 m. As this is a long, uniform beach extending for
100 km, it may give a better estimate of the scale
of the stranding than Makara Bay, which could have
accumulated specimens drifting south-east. The
prevailing strong to gale winds over the previous two
weeks had been from the north-west. As at Makara,
dead Velella were piled about 100 mm thick and metres wide over the entire length of Pukerua Bay
(41°02'S 174°54'E), in contrast to the few individuals found each year for the past 17 years, and
comprised two main strandings about a week apart (M.J. Meads, personal communication).To check
how widespread the stranding was, members of the New Zealand Ornithological Society Beach
Patrol, who walk tidelines regularly throughout New Zealand counting dead birds, were contacted.
They reported far larger numbers of Velella than usual from Northland, Waikato and Southland, so
apparently the whole of New Zealand was affected.
The maximum length of a random sample of 124 oats (the skeletal part remaining when the
animal dries) was 26.06 mm, 95% condence interval 24.4–27.7, range 11–46 mm. Of this sample 90
(72.6%) were left sailors (i.e. would drift to the left of the wind direction—the discription right and
left handed is preferable to saying the sail runs north-west–south-east or north-east–south-west,
because this reverses depending on whether the observer considers the animal is sailing like a yacht
or drifting sideways, as it does).
DISCUSSION
There are no records of previous mass strandings in New Zealand, although a few Velella drift
ashore every year, especially on Northland beaches (Powell, 1959; Morton & Miller, 1968). Schuchert
(1996) listed all the New Zealand material, and only one of 69 was a left sailor, plus ‘several’ seen in
1994 off Kapiti Island which were all right sailors. In contrast, 72.6% in the present mass stranding
were left sailors.
In North America mass strandings occur on Pacic beaches occasionally, and may deposit up to
2.5 kg ash-free dry weight per metre of shoreline (Kemp, 1986). The distribution of Velella appears
to be extending north in the northern hemisphere, reaching Millport Marine Station in the west
Figure 1. A typical section of the tide-line at Makara Bay. Width of photograph 1.2 m.
J.E.C. Flux First mass stranding of Velella velella in New Zealand
JMBA2 - Biodiversity Records
Published on-line
2
of Scotland in 2002 (www.marlin.ac.uk/Velellavelella.htm). According to Lynam et al. (2005) jellysh
abundance is increasing in numerous marine ecosystems worldwide, and if this is associated with a
temperature rise, or stormy weather, caused by global warming, or over-shing, it may be useful to
document mass strandings as an index of future changes.
I thank Mike Meads and members of the Ornithological Society for information on strandings, and Lisa
Gershwin and Dennis Gordon for helpful comments and access to literature.
REFERENCES
Kemp, P.F., 1986. Deposition of organic matter on a high-energy sand beach by a mass stranding of the cnidarian
Velella velella (L.). Estuarine, Coastal and Shelf Science, 23, 575–579.
Lynam, C.P., Hay, S.J. & Brierley, A.S., 2005. Jellysh abundance and climatic variation: contrasting responses in
oceanographically distinct regions of the North Sea, and possible implications for sheries. Journal of the
Marine Biological Association of the United Kingdom, 85, 435–450.
Morton, J. & Miller, M., 1968. The New Zealand sea shore. London, Auckland: Collins.
Powell, A.W.B., 1959. Native animals of New Zealand. Auckland: Unity Press.
Schuchert, P., 1996. The marine fauna of New Zealand: athecate hydroids and their medusae (Cnidaria:
Hydrozoa). New Zealand Oceanographic Memoir, 106, 1–159.
Submitted 11 June 2007. Accepted 24 July 2007.
... Velella velella Linnaeus, 1758, commonly known as the by-the-wind sailor , is a pleustonic, open ocean species found globally in tropical and temperate oceans (Daniel 1976, Bieri 1977, McGrath 1985, Evans 1986, Mianzan & Girola 1990, Flux 2008, Gul 2015. It is a holopelagic colonial anthoathecate hydrozoan belonging to the family Porpitidae. ...
... Velella velella is renowned for forming huge rafts at sea and for massive beach strandings that have been reported in many of the world s oceans (Evans 1986, Flux 2008, Purcell et al. 2015, Pires et al. 2018) and may deposit up to 2.5 kg ash-free dry weight per metre of shoreline (Kemp 1986). This highlights its importance in open-ocean carbon cycling and in transport of pelagic production to landmasses (Purcell et al. 2012). ...
... drift to the right in the downwind direction, Calder 1988, Fig. 2B). This form is less commonly observed than the left-sailing form, with most of the sightings occurring on the western shores of the southern hemisphere (Flux 2008, Araya & Aliaga 2018. The presence of V. velella in the Bay of Ranobe may be the result of Southeast Trade Winds that blow every day during the austral winter. ...
Velella velella (Cnidaria: Hydrozoa) in the Bay of Ranobe, south-west Madagascar
Article
Full-text available
  • Aug 2019
Velella velella widely occurs in the tropical and temperate oceans of the world and the number of mass strandings of colonies is increasing. Although its historical presence in the south-western Indian Ocean is known, recent observations are limited to Tanzania, Mauritius and South Africa. This is the first record of V. velella from Madagascar and the Mozambique Channel since 1964. Given the perceived increase in gelatinous zooplankton abundance, the lack of recent reports from this area highlights the need to monitor its presence to help coastal communities face the negative consequences of potential blooms.
... Indeed, reports of these large strandings account for much of the data available about Velella abundance, density, and movement dynamics. During a documented mass stranding in New Zealand in October-November 2006, a subsidy of approximately 100 million individual Velella were delivered to a six-kilometer stretch of beach ecosystem (Flux 2008). For the almost two decades prior to the 2006 New Zealand stranding, only a few individuals per year washed up on the same beaches (Flux 2008). ...
... During a documented mass stranding in New Zealand in October-November 2006, a subsidy of approximately 100 million individual Velella were delivered to a six-kilometer stretch of beach ecosystem (Flux 2008). For the almost two decades prior to the 2006 New Zealand stranding, only a few individuals per year washed up on the same beaches (Flux 2008). Kemp (1986) documented similar mass strandings on beaches around Newport, Oregon, in 1981Oregon, in and 1984Oregon, in , with only scattered stranded individuals in 1982Oregon, in , 1983Oregon, in , and 1985. ...
... During strandings in 1984, an estimated 2573 g of ash free dry weight/m of shoreline (1223 g/m carbon, 347 g/m nitrogen) stranded on the beach. During a recent beach stranding in New Zealand, as many as 25,000 individuals/m 2 were deposited (Flux 2008). As an individual prey item, Velella provide approximately 2.9 kJ energy/g dry mass (with an individual Velella weighing an average of approximately 0.09 g dry mass) and are likely among the gelatinous organisms that are energetically cheap for predators to capture and digest (Arai et al. 2003). ...
Coastal marine ecosystem connectivity: pelagic ocean to kelp forest subsidies
Article
Full-text available
  • Feb 2019
The movement of trophic resources between and among ecosystems, referred to as cross‐ecosystem subsidies, is a common phenomenon. In the marine environment, both adjacent and distant ecosystems are connected by oceanographic forces that transport nutrients, organisms, and other materials. Kelp forest ecosystems are one example of an open marine system that both exports and receives trophic subsidies. Though rocky reefs are rich in kelp‐based energy produced internally, kelp forest organisms also rely on phytoplankton, and the influx of holoplankton and meroplankton from adjacent open ocean habitats. In this paper, we seek to clarify the identity of holoplanktonic and meroplanktonic subsidies, quantify their energetic and nutrient contributions to the kelp forest, and further explore the impacts of these subsidies for individual consumers and for kelp forest communities. We reviewed six individual subsidy organisms that are commonly advected to kelp forests on the West coast of North America, and show that these organisms from the pelagic ocean represent important resource pulses for kelp forest consumers. In addition, we summarize the characteristics of subsidies, consumers, and recipient ecosystems that provide insight into the dynamics of subsidy influx and impacts to recipient systems. Finally, we provide suggestions as scientists move forward with efforts to quantify the impacts of cross‐ecosystem subsidies. Trophic subsidies are a major force shaping both marine and terrestrial communities and ecosystems. Quantitative information about these subsidies and their impacts on food webs will not only improve our understanding of these ecosystems, but also improve food web models, and predictions of ecosystem response to change.
... Velella velella (Linnaeus, 1758), commonly known as by-the-wind sailor, is a cosmopolitan holoplanktonic, free-floating marine hydrozoan living in open waters at tropical and temperate latitudes (Daniel 1976;Bieri 1977;McGrath 1985McGrath , 1994Evans 1986;Mianzan & Girola 1990;Flux 2008;Gershwin et al. 2010;Purcell et al. 2015;Gershwin 2016;Pires et al. 2018). The polymorphic colony, up to 120 mm long (Bieri 1977), is enclosed in an oval chitinous pneumatophore, positively buoyant and characterized by an upright and triangular dorsal sail. ...
... This trend can be also seen comparing the two consecutive strandings in Santa Margherita Ligure. The average size of the last stranded colonies is in agreement with that recorded from the Atlantic Ocean in 2013 and 2014, (33 mm and 32 mm, respectively), and slightly larger in respect to that measured by Flux (2008) from New Zealand (average 26 mm). ...
Massive strandings of Velella velella (Hydrozoa: Anthoathecata: Porpitidae) in the Ligurian Sea (North-western Mediterranean Sea)
Article
Full-text available
  • Jan 2019
Velella velella, the so-called by-the-wind sailor, is a common member of the open-ocean pleustonic fauna, worldwide distributed in tropical and temperate regions. Thanks to their sail protruding above the sea surface, floating polymorphic colonies of this hydrozoan are carried by winds, and tend to aggregate in large swarms, that often get stranded along the shores. Although these events are commonly observed in springtime along the Ligurian coasts (North-western Mediterranean Sea), no quantitative characterization was ever made. The aim of this study was to characterize the stranding events that occurred in spring 2016 along the Ligurian coast, by evaluating the influence of the local sea conditions and by quantifying the abundance of the stranded colonies in each event. Their size-frequency distribution and biomass were examined, and the associated mollusc fauna identified and counted. The magnitude of these episodes was so relevant that, along the Ligurian coasts, the V. velella strandings constitute one of the most important biological deposition of organic matter; nevertheless, the ecological role of these remarkable and stochastic accumulations of chitin along the coast is still unexplored.
... Particular patterns of physical processes, such as currents and winds, may also promote and enhance jellyfish aggregations along coastal areas ). This may lead to mass stranding events as are common in pleustonic gelatinous organisms, such as Physalia physalis, Velella velella and Glaucus atlanticus (Flux 2008, Pietro et al. 2015, Pinotti et al. 2019, large scyphomedusae , Canepa et al. 2014, small calycophoran siphonophores (Guerrero et al. 2018), and hydroids (Genzano et al. 2008). Although the role of biological production and physical transport is unquestionable, behavioral factors, such as oriented swimming, known particularly in large medusae, may also enhance aggregations (Zavodnik 1987, Shanks and Graham 1987, Fossette et al. 2015. ...
Gelatinous zooplankton
Chapter
  • Dec 2021
Gelatinous zooplankton (GZ) is a non-taxonomic term for jelly-like organisms that have a high proportion of water in body tissues. Advantages in being gelatinous include better buoyancy, transparency, larger sizes with lower carbon investment, rapid growth and body plasticity. Most GZ taxa have different pathways of asexual reproduction that may quickly boost their populations. Thus, many GZ are opportunistic-colonizing species that rapidly increase their populations in response to favorable conditions, often resulting in extensive agglomerations (i.e., blooms). The bloom dynamics depends on multiple environmental drivers, such as increased temperature, food availability, predation, eutrophication, etc., and can be enhanced by physical transport. GZ blooms have implications for vertical flux of particulate matter via production of fecal pellets and carcasses. Feeding mechanisms and trophic niches of GZ are diverse, ranging from filter-feeding very small particles to voracious predators. In any case, GZ are known for their high feeding rates that can impact prey populations. GZ have been historically considered trophic dead ends; however, a variety of animals feed occasionally, regularly, or exclusively on these organisms, including other GZ, mollusks, crustaceans, fish, turtles, birds and humans. The large bodies of GZ species offer microhabitats for numerous organisms ranging from virus and bacteria to crustaceans and fishes. Possible advantages to symbionts include protection from predators, transport, and food supply. Human activities have modified marine ecosystems. While some GZ species may benefit from these modifications, shelled mollusks may face physiological constraints that may preclude their existence. It has been hypothesized that GZ blooms are increasing globally, in response to anthropogenic stressors such as climate change, eutrophication, hypoxia, and overfishing. Although GZ blooms have been recurrently reported and some species may thrive in conditions that are detrimental to other metazoans, evidence to support a global GZ increase is relatively weak when compared to evidence supporting the existence of other changes in marine environments (e.g., overfishing). Most data on GZ are spatially, temporally, and taxonomically limited, cover few populations, and cannot account for the role of multiple natural drivers (e.g., ocean-atmosphere oscillations).
... V. velella distribution is quite unpredictable; it has a seasonal distribution, being the warmer periods when they occur, grow and reproduce more (Bieri, 1977;Purcell et al., 2012), possibly due to food and light availability and wind conditions (Bigelow, 1911;Bieri, 1977;Purcell et al., 2015); the ocean circulation and the wind regimes also contribute to their erratic dispersal (Bieri, 1977). The species is responsible for huge blooms and mass stranding throughout the world's oceans (Evans, 1986;Flux, 2008;Purcell et al., 2015). Those large blooms can reach the shore and impact the coastal systems as they are responsible for the deposit of big amounts of nitrogen and carbon (Bieri, 1977;Purcell et al., 2015;Savilov, 1968). ...
Medusozoans reported in Portugal and its ecological and economical relevance
Article
  • Mar 2020
Cnidaria is a phylum of predominantly marine organisms that evolved into two basic body forms: “polyp” characterized by a tubular body; and “medusa” the free-floating stage characterized by a bell-shaped body. A fast increase in the abundance of the free-living stage of cnidarians known as “jellyfish”, can produce huge impacts on fisheries, public health, tourism, and the normal functioning of factories and aquaculture. Those mass occurrence events are influenced by some natural factors such as water temperature, wind and water tides, but also induced by global warming, overfishing, eutrophication and widening of invasive species habitats. These events have also been reported in the Portuguese coast, but the information is still scarce and therefore their impacts are underestimated. Herein, we provide an updated list of medusozoans in mainland Portugal and archipelagos, and their available genetic information. The data gathered showed a total of 272 medusozoans species comprising 254 hydrozoans, 15 scyphozoans, 2 staurozoans, and 1 cubozoan. The data compiled revealed that 26 % of the reported species did not present any genetic information in public databases (May 2019). Moreover, most of these sequences belonged to the mitochondrial markers 16S ribosomal RNA (16S rRNA) and cytochrome c oxidase subunit I (COX1), and to nuclear markers 18S ribosomal RNA (18S rRNA) and 28S ribosomal RNA (28S rRNA). However, the behavior of the medusozoans registered revealed that the hydrozoans Blackfordia virginica, Physalia physalis, Velella velella and the scyphozoans Aurelia aurita, Catostylus tagi, Pelagia noctiluca and Rhizostoma luteum can produce mass occurrence events. Hence, far more than an updated list of medusozoans species in Portugal, and their genetic information, we revealed the species of medusae more capable of provoking events of mass occurrence that could suddenly affect the dynamic of the ecosystems.
... We consider monitoring and recording of cnidarian stranding events of importance, since they may give information on life cycles, seasonality, spatial distributions, and historical occurrence (Houghton et al. 2007;Kienberger and Prieto 2017), especially in highly productive and biologically important areas such as the Strait of Gibraltar (Gómez et al. 2004;Navarro et al. 2011) where zooplanktivorous siphonophores may have a considerable trophic role (Purcell 1982;Pagès et al. 2001). Furthermore, some authors have pointed out the usefulness of documenting mass strandings as an index of future global changes (Flux 2009). ...
First record of beaching events for a calycophoran siphonophore: Abylopsis tetragona (Otto, 1823) at the Strait of Gibraltar
Article
  • Oct 2018
Two beaching events of the calycophoran siphonophore Abylopsis tetragona (Otto, 1823) were observed in two different areas of the Strait of Gibraltar during the cold season. The first was discovered on November 2014, on Getares Beach (Algeciras Bay, Mediterranean part of the Strait of Gibraltar), where more than 700 colonies were found deposited along the tideline. The second event was discovered on January 2015, on Paloma Baja Beach (Tarifa, Atlantic part of the Strait of Gibraltar) where an average density of 170 colonies m⁻² was spread along the seashore. Both events seemed to be promoted by strong easterly winds, preceded by upwelling episodes that may have concentrated high densities of the siphonophore in superficial layers. This study represents the first report of a calycophoran siphonophore mass stranding. The records were made thanks to citizen science and jellyfish outreach at secondary schools (PERSEUS@school initiative), illustrating the importance of citizen science projects in observing natural phenomena. We consider the monitoring and recording of cnidarian stranding events especially important in highly productive and biologically active areas such as the Strait of Gibraltar.
... Their presence at the sea surface makes them a conspicuous component of the pleuston (Cheng 1975), particularly when high abundances occur in tropical and temperate oceans. Mass strandings of colonies and huge rafts at sea have been reported in many of the world's oceans (Evans 1986;Flux 2009;Purcell et al. 2015;Pires et al. 2018). In the NE Pacific, these blooms and distribution patterns depend on a variety of factors including wind, food availability, growth, and mortality (Mackie 1962;Bieri 1977). ...
Trophic ecology of the neustonic cnidarian Velella velella in the northern California Current during an extensive bloom year: insights from gut contents and stable isotope analysis
Article
Full-text available
Aggregations of the neustonic hydrozoan Velella velella occur periodically in the northern California Current. Despite the regular occurrence of notable bloom events in this productive upwelling zone, little is known about their trophic ecology. We used gut content and stable isotope analyses (SIA) to elucidate V. velella prey selectivity and trophic niche to address their potential impacts on the marine ecosystem. The dominant prey items ingested by V. velella colonies were non-motile prey including cladocerans and northern anchovy (Engraulis mordax) eggs, though copepods were also common in gut contents. Removal rates of northern anchovy eggs could be magnified in bloom years and in areas of high spawning biomass. Stable isotope analysis revealed differences in isotopic niche width and overlap among V. velella based on latitudinal gradients and to a lesser extent on V. velella size and demonstrates the need for continued work to fully understand the trophic ecology of this unique neustonic organism.
... Velella velella (Linnaeus) is an unusual surface-dwelling cnidarian found globally in tropical to temperate open ocean waters (reviewed in Daniel, 1976;Bieri, 1977;McGrath, 1985;Evans, 1986; see also Mianzan and Girola, 1990;Flux, 2008). It is a holopelagic anthomedusan species with a floating colonial polyp stage and an upright chitin sail. ...
Digestion and predation rates of zooplankton by the pleustonic hydrozoan Velella velella and widespread blooms in 2013 and 2014
Article
Full-text available
Surface-dwelling colonies of Velella velella occur throughout tropical to cold-temperate oceans of the world and sometimes are stranded in masses along hundreds of kilometers of beaches. Large-scale blooms in the Western Mediterranean Sea in 2013 and 2014 allowed the study of diet, prey digestion times and predation rates. Gastrozooid content analyses showed that 59% of the 769 identified prey were euphausiid larvae (calytopsis and furcilia) captured at night. Copepods (41%), fish eggs (2.2%) and larvae (0.5%) were captured both at day and night. Digestion times at ambient temperature (∼17°C) of calytopsis, furcilia and copepods were estimated to be >6.5, 4.4 and 3.9 h, respectively. Estimated prey consumption was substantially lower in 2014 than in 2013 (41 vs. 75 prey day−1 colony−1). Velella velella and other gelatinous species bloomed in the Mediterranean Sea and the northeastern Atlantic and Pacific oceans in 2013 and 2014. Because of the wide distribution of V. velella colonies, their mass occurrences, potential importance as predators and competitors of fish, additional production from symbiotic zooxanthellae and stranding on beaches, they could be important in open-ocean carbon cycling and in transport of pelagic production to landmasses.
... Velella velella (Linnaeus) is an unusual pleustonic cnidarian found globally in tropical to temperate open ocean waters (reviewed in Daniel, 1976;Bieri, 1977;McGrath, 1985;Evans, 1986; see also Mianzan & Girola, 1990;Flux, 2008). It is a holoplanktonic anthomedusan, previously placed in a separate order (Chondrophora) because of its chitinous sail. ...
Foods of Velella velella (Cnidaria: Hydrozoa) in algal rafts and its distribution in Irish seas
Article
Full-text available
  • Jul 2012
The pleustonic hydrozoan, Velella velella, occurs throughout tropical to cold-temperate oceans of the world and sometimes are stranded in masses along hundreds of kilometers of beaches. In June 2009, we encountered algal rafts in the Celtic Sea containing many V. velella that we immediately preserved for gut content analysis. Available prey were enumerated from raft-associated fauna and zooplankton sampled nearby. The identifiable prey (331) in V. velella comprised 78% raft-associated prey (primarily harpacticoid copepods, cumaceans, small fish) and 22% pelagic prey (calanoid copepods, barnacle nauplii, fish eggs). Comparison of ingested with available prey showed selection for fish eggs and small fish, among others; therefore, the null hypothesis, that V. velella consumed all available prey equally, was rejected. Transport by wind and water concentrate Velella spp. in convergences with algal rafts, which suggests that they are important predators of raft—as well as pelagic fauna. A visual survey in September 2004 across the Celtic Sea and beach-stranding data show that V. velella is very abundant in Irish waters at times. Its circumpolar abundance, consumption of pelagic prey and production from symbiotic zooxanthellae, and mass deposition on beaches suggest that V. velella is important in open-ocean carbon cycling and in transport of pelagic production to landmasses.
First record of a by-the-wind-sailor (Velella velella Linnaeus, 1758) in the Galápagos Archipelago - Ecuador
Article
Full-text available
  • Aug 2019
We present the first official record of the by-the-wind-sailor ( Velella velella ) for Ecuador. Twelve individuals were found along different beaches of San Cristóbal and Santa Cruz Islands in Galápagos Archipelago, Ecuador. These sightings may be influenced by El Niño Southern Oscillation events.
Jellyfish abundance and climatic variation: Contrasting responses in oceanographically distinct regions of the North Sea, and possible implications for fisheries
Article
Full-text available
Jellyfish medusae prey on zooplankton and may impact fish recruitment both directly (top-down control) and indirectly (through competition). Abundances of Aurelia aurita, Cyanea lamarckii and Cyanea capillata medusae (Scyphozoa) in the North Sea appear to be linked to large-scale inter-annual climatic change, as quantified by the North Atlantic Oscillation Index (NAOI), the Barents Sea-Ice Index (BSII) and changes in the latitude of the Gulf Stream North Wall (GSNW). Hydroclimatic forcing may thus be an important factor influencing the abundance of gelatinous zooplankton and may modulate the scale of any ecosystem impact of jellyfish. The population responses are probably also affected by local variability in the environment manifested in intra-annual changes in temperature, salinity, current strength/direction and prey abundance. Aurelia aurita and C. lamarckii in the north-west and south-east North Sea exhibited contrasting relationships to change in the NAOI and BSII: north of Scotland, where the North Sea borders the Atlantic, positive relationships were evident between the abundance of scyphomedusae (data from 1974 to 1986, except 1975) and the indices; whereas west of northern Denmark, a region much less affected by Atlantic inflow, negative relationships were found (data from 1973 to 1983, except 1974). Weaker negative relationships with the NAOI were also found in an intermediate region, east of Scotland, for the abundance of A. aurita and C. capillata medusae (1971 to 1982). East of Shetland, the abundance of jellyfish was not correlated directly with the NAOI but, in contrast to all other regions, the abundances of A. aurita and C. lamarckii (1971 to 1986, not 1984) were found to correlate negatively with changes in the GSNW, which itself was significantly positively correlated to the NAOI with a two year lag. On this evidence, we suggest that, for jellyfish, there exist three regions of the North Sea with distinct environmental processes governing species abundance: one north of Scotland, another east of Shetland, and a more southerly group (i.e. east of Scotland and west of northern Denmark). Impacts by jellyfish are likely to vary regionally, and ecosystem management may benefit from considering this spatial variability.
The marine fauna of New Zealand: athecate hydroids and their medusae (Cnidaria: Hydrozoa)
Article
Full-text available
  • Jan 1996
1996, The marine fauna of New Zealand: athecate hydroids and their medusae (Cnidaria: Hydrozoa), 12786
The New Zealand sea shore
Article
  • Oct 1968
Powell's Native Animals of New Zealand (4th ed.)
Book
  • Jan 1998
Deposition of organic matter on a high-energy sand beach by a mass stranding of the cnidarian Velella velella (L.)
Article
  • Oct 1986
Strandings of cnidaria occur commonly on exposed shorelines. In some years, large numbers of the chondrophoran Velella velella (L.) are stranded on Pacific beaches of North America. The quantity of organic material deposited on an Oregon beach by one of three mass strandings in 1984 was measured. An average of 2573 g ash-free dry weight (AFDW) was deposited per meter of shoreline, representing 1223 g m−1 of carbon and 347 g m−1 of nitrogen. No significant reduction in AFDW m−1 of the decomposing material was observed in the first three days. The drying mat of stranded material was broken apart by wave action after nine days and most of the material was absent after twelve days. Measurement of microbial and primary production in the period following a stranding may help to determine how long nutrients derived from the stranded material are retained in the beach and surf system.