Snails in IB – Alert the Media?

VIP Beth received these photos from a friend in Imperial Beach last week. They show lots of Wavy Turban Snails washed up on the beach.

Beth was asking if anyone knew why and if we were seeing the same thing at Cabrillo.

During the recent cleanup in the tidepools, the TPERPS said they are not seeing this at Cabrillo which is good.

No one seems to know what is causing this. Perhaps it is from the cross border sewage pollution. Any thoughts from anyone? Leave a comment below.

6 thoughts on “Snails in IB – Alert the Media?

  1. TPERP Gayle reached out to some of her Scripps contacts. Here are their thoughts.

    Well, I am not a biologist so I am not the best to ask! I am cc’ing Carlos who has done the benthic work on the project I’m on that looks at some coupled physical-biological response to the red tide.

    Were the photos taken last week or is it possible they were taken earlier? Zach showed some very similar pics that were taken at IB that I think were during the red-tide event? It is hard to say when the red-tide event (and its consequences) ended, it seems to have continued to cause issues through mid May in most places, and into late May in a couple of places (but due to extenuating circumstances, such as in Los Penasquitos Lagoon). Hypoxic conditions were observed around SIO pier ~May4-8th or so (the same time when large numbers of fish and invertebrates died in the SIO and NOAA aquaria that were sucking in water from the pier) and inside the Tijuana Estuary April 29th-May 4th. Massive benthic species die-offs were observed in the local estuaries from approximately early to middle of May. Interestingly in a recent video conference about the red tide, some of the biologists were suggesting it was not actually the low DO conditions, but possibly other co-occurring conditions that led to the deaths.

    This is also the time of year for periodic upwelling in the region which can bring lower DO water closer to the surface… but I don’t know the exact timing of recent upwelling events and if any were strong enough to impact benthic organisms.

    IB certainly experiences not just the larger oceanic conditions like the red-tide and upwelling, etc, but also impacts and stressors from the local pollution sources as mentioned in that email chain. Waves in much of May and June have been largely from the South and West (depending on their frequency). Waves from the south drive northerly currents in the surfzone which would transport any pollutants from southern sources (e.g., either the Tijuana River and/or Punta Bandera) northwards towards IB. Although the strength of those currents (and thus how far they can carry things) is related to the wave height, and the waves have not been very large (as is typical for this time of year). The outflow from the Tijuana River has been small this month, but non-zero, and PB flows consistently year round. Falk Feddersen, cc’d may be able to give an estimate of whether the wave-driven currents have been strong enough to bring pollution from either of those point sources to IB. But whether those waters have stuff in them at concentrations high enough to kill these snails, I really do not know (I don’t know anything about those snails, nor what is dangerous to them, nor what exactly is in those sources).


    To answer the question: I’m not sure either. To mimic Sarah’s response here are some possibilities:

    1) It is possible it is red tide related. In early- to mid-May we received reports of wavy top turban snail strandings in IB that corresponded with the low oxygen events caused by the red tide. Physiological changes from poor water quality (more particulates, ammonia, hydrogen sulfide, etc.) can deteriorate an organism’s health over a longer period of time so it is possible that this is a delayed effect of the red tide. However, we haven’t received any similar reports for June.

    2) It is possible that hypoxic conditions brought on by localized upwelling led to this die off (in a similar manner to the hypoxic events of the red tide).

    3) I don’t know much about Megastraea but it could be related to life history. From what I understand, females die after brooding eggs and the eggs hatch in the Spring. However, I do not know if mass mortality like that is common or whether it happens in IB annually.

    4) Some alternative reason (e.g., pollution).

    Sorry, I can’t definitively provide an answer.

    This is a really good discussion, and has certainly brought up some good ideas.

    My friend said the photos were from June 10, 2020.

    From back in my days as a biologist, I know that Megastraea lives on rocky substrate, like subtidal reefs, and grazes on algae growing on the rocks. It also lays its egg capsules on the rocks. They live a relatively long time (decades I believe), and so can lay eggs for many years.

    I’m thinking the deteriorating water quality due to the dinoflagellate die-off as well as other organisms dying due to low DO, could contribute over days or weeks to poor water quality near the bottom. I was surprised seeing sand dollars and sea pansies washing up on La Jolla Shores and Scripps’ beaches, so perhaps the Megastraea die off has a similar cause.

    If anyone else has other information, it would be good to hear it.

    Thanks so much for the great input!


  2. Thanks for this!
    I walk down to the TJ River mouth in the evening, and have been noticing these the past few nights.
    Not as many as in the above pics though. The pics look to be more North from where I walk.

    The info in the above comment is very enlightening, and appreciate the multiple theories. Obviously many factors go into determining something like this.

  3. I was just walking IB by the ymca towards Coronado.. since there’s usually not a lot of people on the side.. and there’s was still a lot of those washing up.. big fat healthy ones too. I felt bad.. I think it could be because of the pollution. But who knows :/ . I lived here my whole life and never seen them wash up like this..

  4. Hi there。Found this page while trying to find out the same info. Saw loads of these shells today in IB by the estuary. Magnificent shells. Many still had the body/foot on and some still alive. I don’t think this is a regular occurrence because the birds left the snails alone (unlike sand dollars when they wash up on the shore).

  5. There was a mass die off in Mendocino county, van damme beach, that we saw yesterday. Did anyone find out the answer definitively? So far this site is the only place I’ve found mention of this phenomenon…


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