Arxiu de la categoria: Marine mammals: Ecology and population biology

What lies beyond the death of a whale?

Have you ever wondered what happens after the death of a whale? When a whale’s life ends, its body turn into a new ecosystem for many life forms. Do you want to learn more about whale falls? Which are the stages of a whale fall? Do you want to discover some incredible new species? 

INTRODUCTION

Whales are amazing animals and they play a significant role in the marine ecosystems, as well as other cetacean species. Take the humpback whale for instance. This species feeds using a unique system called the net bubble method, in which seabirds can take advantage of it due to the fact that whales drive prey to the surface. Another key role they play is the transport of nutrients. Finally, another example is the one that we are going to explain in this post: the whale falls.

WHAT IS A WHALE FALL?

Whale corpses are known to serve as a host for animals that live in the bottom of the oceans. When the whale carcasses fall to the bottom of the sea, concretely in the bathyal or abyssal zone (at depths of 2,000 m or more), they are called whale falls. These animals take benefit from the dead whales since they serve as a source of food for them.

Whale fall (Picture: Ocean Networks).
Whale falls are ecosystems by themselves (Picture: Ocean Networks).

It is believed that whale falls may have provided a stepping stone for deep-sea species to colonise the sea floor. In addition, the more research, the more new species described and the more potential commercial applications.

STAGES OF COLONIZATION

A dead whale creates by itself a new and rich ecosystem because produces intense organic enrichment in a very small area. After this, successive stages of colonization take place. Species found in these areas are similar to those in hydrothermal vents. According to researchers, whale falls pass through three stages:

  1. Mobile scavengers stage
  2. The enrichment-opportunist stage
  3. Sulfophilic stage
Decomposition of a whale carcass in Monterey Canyon over 7 years (Picture: MBARI).
Decomposition of a whale carcass in Monterey Canyon over a 7-year period (Picture: MBARI).

It is thought that tens of thousands of organisms from about 400 animals species depend on a single whale fall. Astonishingly, scientists estimate that one whale corpse provides with the nutritional equivalent of 2,000-years worth of normal biological detritus sinking to the seafloor.

1. MOBILE SCAVENGERS STAGE

The first stage is dominated by mobile scavenger species. In this stage, the dead whale is covered by a dense aggregaton of hagfishes, small numbers of lithodid crabs, rattail fish, large sleeper sharks and millions of amphipods.

These animals are responsible of the disappearance of the soft tissue. They can eat 40-60 kg per day. In a 5-ton carcass, it lasted for 4 months, while in 35-tone carcasses for 9 months to 2 years.

Grey whale decomposition, 2 month after deposition (Picture: Hermanus Online).
Grey whale decomposition, 2 and 18 month after deposition (Picture: Hermanus Online).

2. THE ENRICHMENT-OPPORTUNIST STAGE

During the second stage, the animal’s skeleton is surrounded by dense aggregations of polychaete worms, cumaceans (crustaceans) and molluscs such as snails. There have been described some whale fall specialist species, previously unknown. These animals feed on the rest of the body, including the sediment surrounding because it is full of decomposing tissue.

Se (Picture: Hermanus Online).
During the enrichment-opportunist stage, the skeleton is surrounded by many species of animals (Picture: Hermanus Online).

3. SULFOPHILIC STAGE

This is by far the longest stage in whale falls: it might last from 10 to 50 years, or more. The so-called sulfophilic stage owes its name to the sulfide produced by bones due to the action of chemosynthetic bacteria, who use sulfate to break down the lipids inside the bones and produce sulfide. The sulfide allow the presence of dense bacterial mats, mussels and tube worms, among others. It have been found more than 30,000 organisms in a single skeleton.

Sulfide stage (Picture: Hermanus Online).
Sulfophilic stage (Picture: Hermanus Online).

NEW SPECIES DISCOVERED

As it has been mentioned above, new species have been described in whale falls. In this section, we are going to present only some of them.

The anemone Anthosactis pearsea is a small, white and cube-shaped species. Its importance lies on the fact that it is the first anemone found on a whale fall.

df (Picture: MBARI).
Anthosactis pearseae (white animals) (Picture: MBARI).

Species included in the genus Osedax have also been discovered. Their common name, bone-eating zombie worms, reflects exactly their task: to eat bones. These animals have neither eyes nor mouth, but they present reddish plumes that act as gills and some kind of green roots, where symbiotic bacteria break down proteins and lipids inside the bone, which supply nutrients for the worms. The macroscopic form of the animals is always a female, who contains dozens of microscopic males inside its body

Osedax frankpressi (Picture: Greg Rouse).
A female Osedax frankpressi (Picture: Greg Rouse).

Another strikingly awesome worm is the bristleworm, Ophryotrocha craigsmithi. In spite of lacking any particular adaptation, it is thought that they are exclusive at whale falls or similar ecosystems.

Ophryotrocha craigsmithi (Picture: Live Science)
Bristleworm, Ophryotrocha craigsmithi (Picture: Live Science)

A final example to take into consideration is the gastropod Rubyspira, whale-fall specialists molluscs which are 3-4 cm in length.

Rubyspira snails on whale bones (Picture: MBARI). Lat= 36.61337280 Lon= -122.43557739 Depth= 2895.4 m Temp= 1.683 C Sal= 34.618 PSU Oxy= 2.31 ml/l Xmiss= 84.1% Source= digitalImages/Tiburon/2006/tibr991/DSCN8049.JPG Epoch seconds= 1148489479 Beta timecode= 07:21:57:03
Rubyspira snails on whale bones (Picture: MBARI).

I encourage you to watch these videos about whale falls. In the first one, you can see a diving on the Rosebud whale fall carried out by the team of E/V Nautilus, searching for the life it supports. In the second one, you can see a feast in the deep in a whale fall in Monterey Canyon, recorded by the Monterey Bay Aquarium Research Institute (MBARI).

REFERENCES

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Anuncis

Breeding in seals and social organitzation

Pinniped species, commonly known as seals, breed on land or ice. Depending on the place they breed on, they present a social organization or another. In this post, we will review both the breeding systems in seals and their social organization. Do you know that in the Mediterranean Sea live seals? 

MATING AND BREEDING IN PINNIPEDS

Pinnipeds have different mating systems: while most of the species are polygynous, it is that males mate with several females; others are monogamous and males mate with just one female during a breeding season. In the first case, males are much larger than females, while in the monogamous system there are almost no differences between sexes.

Like in the rest of species, females are more valuable than males because they produce the ovule, carry and nourish the young, produce milk after birth and provide all parental care. On the other side, it is much better for males to copulate with as many females as possible to increase their reproductive success. Therefore, maternal nurturing plays a key role in organising their societies. 

Pinnipeds use different habitats for their breeding:

  1. Land
  2. Ice: both pack ice (floating ice) and fast ice (ice attached to land).

In the following sections, we will explain the mating and breeding systems in each type of seal, in addition to their social organization.

LAND-BREEDING SEALS

20 of the 33 pinniped species breed on land, specially on islands because are more favourable than mainland beaches and sandbars (where they can also breed on).

South-American-sea-lion--bull
South American sea lions (Otaria bryonia) breed on land (Picture: Steven Hazlowski, Arkive).

However, there are neither many favorable islands to seals nor many suitable breeding sites in these islands and, thus, females and pups tend to congregate in colonies, where males either compete for breeding territories (in otariids, it is sea lions and fur seals) or establish dominance hierarchies (in elephant seals). 

Cape-fur-seal-colony
South African and Australian fur seals (Arctocephalus pusillus) live in large colonies (Picture: Pete Oxford, Arkive)

These aggregations let males copulate with a great number of females (after an intense competition among males).

Among the species that breed in large colonies, there are a marked variability in the social organization. Some species form annual breeding aggregations at traditional locations called rookeries. Rookeries are formed by all otariids, elephant seals and gray seals. During this period, females and pups live in zones controlled by alpha males, while juvenile and subdominant males live in bachelor groups.

Even during the nonbreeding season, they  usually live in association with other animals because it gives some advantages:

  • Thermoregulatory effects of huddling together during cold weather.
  • Protection from predators.

ICE-BREEDING SEALS

Different from the land-breeding seals, ice-breeding species on pack ice are not obliged to form aggregations due to the vast available ice and, therefore, males cannot mate with so many females, just one or a few females.

Ross-seal
Ross seal (Ommatophoca rossii) chiefly live on dense consolidated pack ice. They are usually solitary or live in small groups (Picture: NOAA, Creative Commons).

So, it is common in seals that breed on pack ice to be monogamous or slightly polygynous. 

On the other side, seals can breed on fast ice (ice which is attached to land), usually in cracks and open holes. Therefore, they live in small to moderate-sized groups where a male can mate with only some females close to these particular points.

Pusa_hispida_pup
Fast-ice breeding seals, such as ringed seals (Pusa hispida) live in small to moderate-sized groups (Picture: Shawn Dahle, Creative Commons).

In general, ice-breeding seals of both sexes have a similar size, with the exception of the hooded seal (Cystophora cristata) and the walrus (Odobenus rosmarus), in which males are bigger than females; and of the Antarctic Weddell seal (Leptonychotes weddellii), in which females are bigger than males. The reason is that males maintain aquatic territories beneath the ice near holes and cracks and being smaller makes easier to protect territories and mate with females.

Phoque_de_Weddell_-_Weddell_Seal
In Weddell seals (Leptonychotes weddellii), females are bigger than males (Picture: Samuel Blanc, Creative Commons).

CONCLUSION

In conclusion, when the available space is limited, female seals congregate in large colonies, where males can mate with several females; while when the space is dispersed, females are isolated and males can mate with just one female and colonies are not formed.

REFERENCES

  • Acevedo-Gutiérrez, A (2009). Group Behaviour. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Antonelis, GA (2009). Rookeries. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Berta, A (2009). Pinnipedia, Overview. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Mesnick, S. & Ralls, K (2009). Mating Systems. In Perrin, W; Würsig, B & Thewissen, JGM (ed.). Encyclopedia of Marine Mammals. Academic Press (2 ed).
  • Riedman, M (1990). The Pinnipeds. Seals, sea lions and walruses. University of California Press.
  • Shirihai, H. & Jarrett, B (2006). Whales, Dolphins and Seals. A field guide to the marine mammals of the world. Bloomsbury.
  • Main Picture: Ecotrust

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Whale migration is changing due to global change

Results of a research that took place from 1984 to 2010 in the Gulf of St. Lawrence (Canada, North Atlantic Ocean) about changes in migration patters of whales due to global change have been published this March on Plos One. In this post, you are going to find a summary of this article.

INTRODUCTION

Global change (wrongly called climate change) is a planetary-scale change in the Earth climate system. Despite of being a natural process, in the last decades the reason of the changes is human because we have produced an increase of the carbon dioxide’s realise due to fossil fuel burning.

MIGRATION OF WHALES

Global change is a challenge for migratory species because the timing of seasonal migration is important to maximise exploitation of temporarily abundant preys in feeding areas, which, at the same time, are adapting to the warming Earth. Other driving forces are the use of resources like mates or shelter. This is the case of fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaeangliae), which feed on a wide variety of zooplankton and schooling fish. This zooplankton grows due to an increase of phytoplankton, which grows for the increasing light and nutrients during summer. Remember that in this post you can read about the feeding behaviour of humpback whales. This is not the first time that it has been reported changes in migration species’ home ranges in both summer and wintering areas and alterations of the timing.

Fin whale (Balaenoptera physalus) (Picture from Circe).
Fin whale (Balaenoptera physalus) (Picture from Circe).
Humpback whale (Megaptera novaengliae) (Picture from Underwater Photography Guide).
Humpback whale (Megaptera novaeangliae) (Picture from Underwater Photography Guide).

It is observed a general pattern in migratory species: they use high-latitude summer regions to take advantage of high productivity and abundance of their preys and some of them reproduce during this period. Generally, long-distant migrants seem to adapt less well to climate change than short-distant migrants.

humpback whale migration
The case of humpback whale (Megaptera novaeangliae) migration. (Picture from NOAA).

Most baleen whales begin seasonal migrations from few hundreds to thousands of kilometres, alternating between low-latitude winter breeding grounds to high-latitude summer feeding grounds. The response of marine mammals to global change has been predicted:

  • More pole-ward distribution and more beforehand arrival in feeding areas to follow changing prey distribution.
  • Longer residency time in higher latitudes in response to enhanced productivity.

HOW IS GLOBAL CHANGE AFFECTING WHALE MIGRATION?

The article’s results show that fin and humpback whales arrived earlier in the study area over the 27 years of the study. Nevertheless, the rate of change of more than 1 day per year is undocumented. Both species also left the area earlier, as observed in other species. Humpback whale departure changed at the same rate as arrival, so it keeps a constant residency time. On the other hand, fin whales have increased the residency time from 4 days to 20 days. However, that increase is subject to small sample bias in the first two years and there is only weak evidence that fin whales increased their residency time.

Mean first and last sighting date in fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaengliae) (Data from Ramp C. et al. 2015).
Mean first and last sighting date in fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaeangliae) (Data from Ramp C. et al. 2015).

In addition, the results suggest that the region represents only a fraction of the potential summer range for both populations and both species just spend a part of the summer. What is clear is that both species showed the same behavioural adaptation and advanced their temporal occurrence in the area by one month.

Other studies have reported that gray whales (Eschrichtius robustus) have probably ceased to migrate annually in Alaska (Stafford K et al. 2007).

WHY ARE WHALES SHIFTING THEIR MIGRATION PATTERNS?

It seems that fin whale arrival in the Gulf follows the shift in the date of the ice break up and the sea surface temperature (SST) serves as a signal to the whales that it is time to move back into the Gulf. There was a time delay of 13-15 weeks between when this area became totally ice-free and their arrival. This has also seen in Azores, where fin and humpback whales arrive 15 weeks after the start of the spring bloom to feed on it when en route to high latitude summer feeding grounds.

The influence of SST in January in the Gulf may have triggered an earlier departure of humpback whales from the breeding grounds and thus earlier arrival in the Gulf.

These two species of whales are generalist feeders and their arrival in the Gulf is related to the arrival of their prey. The improvement of the temperature and light conditions and earlier ice break-up (together with higher SST) leads to an earlier bloom of phytoplankton followed by the earlier growth of zooplankton. Therefore, the earlier arrival of fin and humpback whales enables timely feeding on these prey species. A 2-weeks time lag between the arrival of fin and humpback whales lets humpback whales fed at a higher trophic level compared to fin whales, what reduces competition.

CONCLUSION

Global change shifted the date of arrival of fin whales and humpback whales in the Gulf of St. Lawrence (Canada) at a previously undocumented rate of more than 1 day per year earlier (over 27 years) thus maintaining the approximate 2-week difference in arrival of the two species and enabling the maintenance of temporal niche separation. However, the departure date of both species also shifted earlier but at different rates resulting in increasing temporal overlap over the study period indicating that this separation may be starting to erode. The trend in arrival was strongly related to earlier ice break-up and rising sea surface temperature, likely triggering earlier primary production.

REFERENCES

This post is based on the article:

  • Ramp C, Delarue J, Palsboll PJ, Sears R, Hammond PS (2015). Adapting to a Warmer Ocean – Seasonal Shift of Baleen Whale Movements over Three Decades. PLoS ONE 10(3): e0121374. doi: 10.1371/journal.pone.0121374

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This publication is licensed under a Creative Commons:

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Parasitology associated to bottlenose dolphin (Tursiops truncatus) [1]: Introduction

This publication is an introduction to bottlenose dolphin (Tursiops truncatus) parasitology. In this publications, there is a list of parasits that they have been found in bibliography and in the next publication we are going to talk about three of them.

The interest on marine mammals’ diseases, mostly on cetaceans, owe to their use on research and entertainment. There is different species of parasits on cetacean, but some of them are accidental parasits that doesn’t cause any serious problem. The following list are the parasits of Tursiops truncatus.

PHYLLUM NEMATODA

Anisakis physeteris Halocercus lagenorhynchus
Anisakis simples Skrjabinalius cryptocephalus
Anisakis typica Stenurus minor
Crassicauda crassicauda Stenurus ovatus

 

PHYLLUM PLATYHELMINTHES

Class Trematoda: Subclass Digenea

Braunina cordiformes         Nasitrema dalli
Campula palliata         Pholeter gastrophilus
Campula rochebruni         Synthesium tursionis
Nasitrema attenuata         Zalophotrema hepaticum

 Class Cestodes

Monorygma delphini
Monorygma Grimaldi
Phyllobothrium delphini

 

PHYLLUM ACANTHOCEPHALA                                        PHYLLUM ARTROPODA

Bolbosoma sp.                                                          Harpacticus pulex
Corynosoma cetaceum                                             Syncyamus sp.

 

PROTOZOA

Holotricha ciliate (not identified)
Cryptosporidium parvum
Giardia duodenalis
Giardia sp.
Kyaroikeus cetarius (ciliate)
Toxoplasma gondii

 

BACTERIA

Actinomyces sp. Nocardia sp.
Aeromonas sp. Pasteurella sp.
Brucilla sp. Pseudomonas sp.
Erysipelothrix sp. Salmonella sp.
Klebsiella sp. Staphylococcus sp.
Lactococcus sp. Streptococcus sp.
Nocardia asteroides Vibrio sp.
Nocardia levis

 

FUNGUS

Blastomyces dermatitidis Histoplasma capsulatum
Candida albicans Lacazia loboi

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