Seaweeds, Sea Urchins, and Lobsters: A Reappraisal

1985 ◽  
Vol 42 (12) ◽  
pp. 2061-2072 ◽  
Author(s):  
Robert J. Miller
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Stomach Contents ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
Sea Otter ◽  
Feeding Rates ◽  
Growth And Survival ◽  
Definition Of ◽  
Urchin Grazing

A popular hypothesis, that on the south coast of Nova Scotia the green sea urchin (Strongylocentrotus droebachiensis) has been released from control by predators, is critically reviewed. Predator control is given the functional definition of limiting sea urchin grazing sufficient to permit abundant growth of seaweed. Of the predators identified, the American lobster (Homarus americanus) is the least likely to have been important in sea urchin control in recent decades. Feeding rates, stomach contents, and field biomass are available for this species. A smaller amount of data available for the rock crab (Cancer irroratus) and benthic feeding fish points to the conclusion that they likewise cannot control urchin populations. Among other temperate sea urchin species the case is strongest for sea otter control of Strongylocentrotus sp. in some areas of the west coast of North America. The formation of sea urchin grazing fronts, a usual step in the destruction of seaweed beds, has been explained as a behavioral response to predators. This may in fact be merely a response to the location of food. Evidence for suspected enhancement of lobster production by seaweeds is equivocal, and comparative field data collected in and out of seaweed beds (e.g. lobster abundance, food, growth, and survival) have not been published.

Effects of the parasitic nematode Echinomermella matsi on growth and survival of its host, the sea urchin Strongylocentrotus droebachiensis

1999 ◽  
Vol 77 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Audun Stien
Keyword(s):  
Population Dynamics ◽  
Sea Urchin ◽  
Parasitic Nematode ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
Probability Models ◽  
Negative Effects ◽  
Growth And Survival ◽  
Host Growth ◽  
Reproductive Rates

It has been suggested that the parasitic nematode Echinomermella matsi significantly affects the population dynamics of its host, the sea urchin Strongylocentrotus droebachiensis. The effects of infection on both host fecundity and host survival may be of importance. The fecundity of sea urchins is related to their size. Negative effects of infection on host growth will therefore reduce reproductive rates. I estimated the effect of infection on host growth and survival in two naturally infected wild sea urchin populations using a capture-mark-recapture approach. Infected and uninfected sea urchins were captured and marked with unique tags or recaptured seven times from June 1994 to September 1996. The increment in the diameter of marked sea urchins between captures was used to measure sea urchin growth. The effect of E. matsi infection on host growth was small. Mortality rates were estimated using survival probability models based on the methodology developed by Cormack, Jolly, and Seber. The effect of infection on host survival was pronounced, with estimated sea urchin life expectancies reduced by 33-86% by E. matsi infection. This suggests that E. matsi may affect the population dynamics of S. droebachiensis significantly through the effect on host survival.

Evidence for Association of Vibrio Echinoideorum with Tissue Necrosis on Body Shell of the Green Sea Urchin Strongylocentrotus Droebachiensis

2021 ◽  
Author(s):  
Jonathan Hira ◽  
Klara Stensvåg
Keyword(s):  
Sea Urchin ◽  
Virulence Genes ◽  
Vibrio Vulnificus ◽  
Sea Urchins ◽  
Opportunistic Pathogen ◽  
Significant Degree ◽  
Strongylocentrotus Droebachiensis ◽  
Host Immune System ◽  
Progressive Development ◽  
Green Sea Urchin

Abstract “Sea urchin lesion syndrome” is known as sea urchins disease with the progressive development of necrotic epidermal tissue and loss of external organs, including appendages on the outer body surface. Recently, a novel strain, Vibrio echinoideorum has been isolated from the lesions of green sea urchin (Strongylocentrotus droebachiensis), an economically important mariculture species in Norway. V. echinoideorum has not been reported elsewhere in association of with green sea urchin lesion syndrome. Therefore, in this study, an immersion based bacterial challenge experiment was performed to expose sea urchins (wounded and non-wounded) to V. echinoideorum, thereby mimicking a nearly natural host-pathogen interaction under controlled conditions. This infection experiment demonstrated that only the injured sea urchins developed the lesion to a significant degree when exposed to V. echinoideorum. Pure cultures of the employed bacterial strain was recovered from the infected animals and its identity was confirmed by the MALDI-TOF MS spectra profiling. Additionally, the hemolytic phenotype of V. echinoideorum substantiated its virulence potential towards the host, and this was also supported by the cytolytic effect on red spherule cells of sea urchins. Furthermore, the genome sequence of V. echinoideorum was assumed to encode potential virulence genes and were subjected for in silico comparison with the established virulence factors of Vibrio vulnificus and Vibrio tasmaniensis. This comparative virulence profile provided novel insights about virulence genes and their putative functions related to chemotaxis, adherence, invasion, evasion of the host immune system, and damage of host tissue and cells. Thus, it supports the pathogenicity of V. echinoideorum. In conclusion, the interaction of V. echinoideorum with injured sea urchins appears to be essential for the development of lesion syndrome and therefore, revealing its potentiality as an opportunistic pathogen.

Destructive Grazing of Kelp by Sea Urchins in Eastern Canada

1976 ◽  
Vol 33 (6) ◽  
pp. 1278-1283 ◽  
Author(s):  
P. A. Breen ◽  
K. H. Mann
Keyword(s):  
Nova Scotia ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Large Contribution ◽  
Eastern Canada ◽  
Kelp Beds ◽  
Urchin Grazing

Destruction of kelp beds by sea urchins has been documented in St. Margaret’s Bay, Nova Scotia, and also appears to be taking place in other parts of eastern Canada. Continued sea urchin settlement onto grazed areas prevents the return of kelp and other algae for long periods. Because of the large contribution of kelp beds to coastal productivity, the disappearance of kelp from large areas is alarming. Dynamics of sea urchin grazing are discussed.

Effect of unidirectional water currents on displacement behaviour of the green sea urchin Strongylocentrous droebachiensis

2013 ◽  
Vol 93 (7) ◽  
pp. 1923-1928 ◽  
Author(s):  
Bryan L. Morse ◽  
Heather L. Hunt
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Flow Speed ◽  
Strongylocentrotus Droebachiensis ◽  
Movement Speed ◽  
Water Current ◽  
Flume Experiments ◽  
Water Currents ◽  
Green Sea Urchin ◽  
The Impact

Sea urchins can have important ecological effects on benthic communities through their aggregation and feeding behaviour. Urchin movement has been demonstrated to be negatively affected by wave action, but the impact of unidirectional tidal currents on urchin movement has not been investigated. This study examines the effect of unidirectional water velocity on the direction of displacement and movement rate of the green sea urchin, Strongylocentrotus droebachiensis. In laboratory flume experiments there was a clear effect of water currents on the displacement of sea urchins. At speeds ≤30 cm s−1 urchins moved across the current in a downstream direction, but at speeds of ≥36 cm s−1 the urchins switched directions by more than 90° and moved across the current in an upstream direction. There was a significant effect of flow speed on urchin movement speed, with urchin movement speed decreasing as water current speed increased.

scholarly journals Depletion of coastal predatory fish sub-stocks coincided with the largest sea urchin grazing event observed in the NE Atlantic

AMBIO ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 163-173 ◽  
Author(s):  
Kjell Magnus Norderhaug ◽  
Kjell Nedreaas ◽  
Mats Huserbråten ◽  
Even Moland
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Local Population ◽  
Population Connectivity ◽  
Strongylocentrotus Droebachiensis ◽  
Predatory Fish ◽  
Ne Atlantic ◽  
Laminaria Hyperborea ◽  
Fish Stocks ◽  
Coastal Fisheries

AbstractIn this contribution, we propose fishery driven predator release as the cause for the largest grazing event ever observed in the NE Atlantic. Based on the evolving appreciation of limits to population connectivity, published and previously unpublished data, we discuss whether overfishing caused a grazer bloom of the sea urchin (Strongylocentrotus droebachiensis) resulting in overgrazing of more than 2000 km2 kelp (Laminaria hyperborea) forest along Norwegian and Russian coasts during the 1970 s. We show that coastal fisheries likely depleted predatory coastal fish stocks through modernization of fishing methods and fleet. These fish were important predators on urchins and the reduction coincided with the urchin bloom. From this circumstantial evidence, we hypothesize that coastal predatory fish were important in regulating sea urchins, and that a local population dynamics perspective is necessary in management of coastal ecosystems.

scholarly journals Effects of elevated temperature and sedimentation on grazing rates of the green sea urchin: implications for kelp forests exposed to increased sedimentation with climate change

2019 ◽  
Vol 73 (1) ◽  
Author(s):  
Sarah B. Traiger
Keyword(s):  
Climate Change ◽  
Elevated Temperature ◽  
Sea Urchin ◽  
Strongylocentrotus Droebachiensis ◽  
Kelp Forests ◽  
Green Sea Urchin ◽  
Kelp Bed ◽  
Elevated Water ◽  
And Shifts ◽  
Urchin Grazing

Abstract Sea urchin grazing rates can strongly impact kelp bed persistence. Elevated water temperature associated with climate change may increase grazing rates; however, these effects may interact with local stressors such as sedimentation, which may inhibit grazing. In Alaska, glacial melt is increasing with climate change, resulting in higher sedimentation rates, which are often associated with lower grazer abundance and shifts in macroalgal species composition. The short-term effects of elevated temperature and sediment on grazing were investigated for the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller, 1776), in Kachemak Bay, Alaska (59° 37′ 45.00″ N, 151° 36′ 38.40″ W) in early May 2017. Feeding assays were conducted at ambient temperature (6.9–9.8 °C) and at 13.8–14.6 °C with no sediment and under a high sediment load. Grazing rates significantly decreased in the presence of sediment, but were not significantly affected by temperature. Along with sediment impacts on settlement and post-settlement survival, grazing inhibition may contribute to the commonly observed pattern of decreased macroinvertebrate grazer abundance in areas of high sedimentation and increased sedimentation in the future may alter sea urchin grazing in kelp forests.

Stomach contents of immature lobsters (Homarus americanus) from Placentia Bay, Newfoundland

1982 ◽  
Vol 60 (3) ◽  
pp. 337-347 ◽  
Author(s):  
J. A. Carter ◽  
D. H. Steele
Keyword(s):  
Sea Urchins ◽  
Stomach Contents ◽  
Late Summer ◽  
Homarus Americanus ◽  
Stomach Fullness ◽  
Natural Diet ◽  
Selection Indices ◽  
Selection For ◽  
Placentia Bay ◽  
High Selection

Stomachs of immature lobsters (Homarus americanus) from Placentia Bay, Newfoundland, were examined to determine natural diet. The most frequently occurring prey were sea urchins, mussels, rock crabs, polynoid and nereid polychaetes, and brittlestars. There was high incidence of lobster exuviae during the moulting period in late summer. Rock crabs, brittlestars, and mussels were dominant (in terms of relative volumes of hard parts in each stomach) more often than other food items. Sea urchins, periwinkles, chitons, rock crabs, and polynoids were consumed more frequently in late summer compared with other seasons. Stomach contents constituted approximately 1% of the wet weight of individual lobsters. There were no significant seasonal differences in stomach fullness during the period June to November.The residencies of natural prey hard parts in immature lobster stomachs were estimated. Some items remained in stomachs for up to 180 days. Measures of stomach fullness of lobsters 3 days after ad libitum feeding on rock crabs, mussels, and sea urchins were similar. Linear selection indices indicated relatively high selection by immature lobsters for hard parts of rock crabs and mussels and positive selection for nereids, polynoids, and brittlestars. Immature lobsters showed negative selection for hard parts of sea urchins, starfish, and periwinkles.

Relationship Between Destructive Grazing by the Sea Urchin, Strongylocentrotus droebachiensis, and the Abundance of American Lobster, Homarus americanus, on the Atlantic Coast of Nova Scotia

1981 ◽  
Vol 38 (11) ◽  
pp. 1339-1349 ◽  
Author(s):  
W. G. Wharton ◽  
K. H. Mann
Keyword(s):  
Population Structure ◽  
Nova Scotia ◽  
Sea Urchins ◽  
Atlantic Coast ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
American Lobster ◽  
History Of ◽  
Kelp Bed ◽  
The Relationship

Relationships between percentage cover of macroalgae, population structure of sea urchins (Strongylocentrotus droebachiensis), and the history of the lobster fishery were examined at nine sites distributed along the Atlantic coast of Nova Scotia from Guysborough County in the northeast to Pubnico in the southwest. At Pubnico there was dense algal cover and a small number of urchins living in crevices, and at Cape Sable there was an area of transition, but at all other sites there were urchin-dominated barren grounds. When the population structure of the urchins was compared with that previously observed in St. Margaret's Bay before, during, and after destruction of beds of kelp (Laminaria spp. and Agarum) by overgrazing, it was concluded that kelp bed destruction occurred on the coast north of Halifax prior to 1970, and on the coast south of Halifax after 1970. From the records of American lobster (Homarus americanus) catches it was concluded that a critical decline in catches at each site occurred a few years after kelp bed destruction. Information from various sources is synthesized into a coherent theory of the relationship between lobsters, other predators, sea urchins, and kelp.Key words: lobsters, Homarus americanus; sea urchins, Strongylocentrotus droebachiensis; destructive grazing, kelp, Laminaria, Agarum

Sea Urchins in the Saint Lawrence Estuary: Their Abundance, Size-Structure, and Suitability for Commercial Exploitation

1983 ◽  
Vol 40 (4) ◽  
pp. 474-486 ◽  
Author(s):  
John H. Himmelman ◽  
Yves Lavergne ◽  
Fritz Axelsen ◽  
André Cardinal ◽  
Edwin Bourget
Keyword(s):  
Growth Rate ◽  
Shallow Water ◽  
Sea Urchin ◽  
Size Structure ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
Lawrence Estuary ◽  
Algal Abundance ◽  
Ice Conditions ◽  
Intermediate Size

Quantitative transects were made at nine locations along the Saint Lawrence Estuary, Québec, to examine changes in the abundance and size-structure of populations of the green sea urchin, Strongylocentrotus droebachiensis, in relation to the estuarine gradient. Near the seaward extremity of the estuary, sea urchin densities are very high and small urchins are particularly abundant in shallow water. In contrast, midway up the estuary, small urchins are scarce in shallow water, probably because they cannot tolerate the periodic drops in surface salinities which occur there. Where urchin densities are high, urchin grazing severely limits algal production, and because of low algal food availability, the urchin growth rate is exceedingly low. In the Upper Estuary, urchin numbers are low and no urchins are found near the surface. There is feeble recruitment of urchins, and the near absence of urchins of intermediate size suggests that there is a high probability that juveniles are killed before they reach intermediate size. The urchin growth rate is accelerated because of the abundance of algae present, and below 10 m deep some juveniles survive through the intermediate size range. After they reach 40–50 mm in diameter, they can move up to the 2- to 10-m-depth zone and can tolerate the periods of hypo-osmotic conditions which occur there. Suitable populations for commercial use are most likely found where salinity or winter ice conditions reduce urchin numbers to a level permitting greater algal abundance and an elevated somatic and gonadal growth of the remaining urchins.

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