Stranding information and microcystin (MCY) concentrations (ppb wet weight) for wild, microcystin-positive sea otters and captive controls.

1<p>nd  =  microcystin concentration was below minimum detection limits on liquid chromatography-tandem mass spectrophotometry.</p

Map of Monterey Bay showing distribution of sea otters dying due to microcystin intoxication (yellow circles).

<p>Note spatial association of sea otter strandings with coastal locations of river mouths, harbors, coastal ponds and embayments. Habitat utilization distributions for 4 radio-tagged, microcystin-poisoned otters are plotted as kernel density distributions fit to daily re-sighting locations (red shading, with regions of most intense shading corresponding to the habitats most frequently utilized by affected animals). Locations of freshwater samples collected during a “Super-bloom” of <i>Microcystis</i> in 2007 are indicated by green circles, with numbers that correspond with the microcystin concentrations listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012576#pone-0012576-g001" target="_blank">Figure 1</a>.</p

Tracing freshwater contamination by microcystins from land-to-sea.

<p>Inset: Sample of surface water collected during a “super-bloom” of <i>Microcystis</i> in Pinto Lake in fall, 2007 (Caution: Nitrile gloves and other appropriate personal protective equipment should be used to prevent dermal contact when collecting environmental samples of <i>Microcystis</i> and microcystins). Main figure: Time-matched microcystin-LA concentrations (ppb) in samples from Pinto Lake, just downstream in Corralitos Creek and the receiving waters of the Pajaro River within 1 km of Monterey Bay. Asterisks (*) indicate sampling locations where <i>Microcystis</i> was detected microscopically.</p

Evaluation of Solid Phase Adsorption Toxin Tracking (SPATT) sampler adsorption characteristics for freshwater microcystins.

<p>SPATT adsorption characteristics for microcystin were tested in the laboratory using Pinto Lake water amended with a known quantity of microcystin-LR. A control sample (open symbols) showed no change in microcystin concentration over time; In contrast, SPATT HP20 resin-based samplers (solid symbols: error bars represent standard deviation of 3 replicates) show rapid microcystin adsorption, with near-total depletion of microcystins from a controlled volume of water within <24 hours.</p

Microcystin detection in sea otter tissues was linked to bivalve consumption, liver damage and icterus.

<p>A.) Wild southern sea otter (<i>Enhydra lutris nerei</i>s) consuming a clam in Elkhorn Slough, Monterey Bay. B.) Diffuse icterus of oral mucous membranes of an otter poisoned by microcystin, due to severe hepatic damage and elevated plasma bilirubin. C.) Severe icterus of cartilage at the costochondral junction in a sea otter that died due to microcystin intoxication.</p

Overlapping home ranges of 4 tagged southern sea otters that died due to microcystin intoxication.

<p>Note the spatial overlap of all 4 home ranges on the north central Monterey Peninsula near Monterey Harbor (bracket): This harbor appears to be one of several high-risk locations for microcystin poisoning of sea otters, possibly due to prolonged retention of microcystin-contaminated water.</p

Microcystin-LR concentrations (ppb) at the top, middle, and bottom of seawater tanks at two exposure concentrations (Tank 2 and Tank 3¹) and varying postexposure intervals.

1<p>All samples from Tank 1 (seawater control) tested negative for microcystin-LR. All 3 tanks were flushed with fresh seawater starting 96 H postexposure).</p>2<p>nd  =  microcystin concentration was below minimum detection limits on liquid chromatography-tandem mass spectrophotometry.</p

Microcystin LR concentrations (ppb wet weight) in marine invertebrate gastrointestinal tissues collected from Tank 3 (high microcystin exposure tank) at various time intervals post-exposure¹.

1<p>All tanks were flushed continually with clean seawater beginning at 96 H post-exposure.</p>2<p>n = 1 or 2 pooled invertebrates of each species at each sample point, except snails, where n = 7.</p>3<p>nd  =  microcystin concentration was below minimum detection limits on liquid chromatography-tandem mass spectrophotometry.</p>4<p>---  =  not tested.</p>5<p>Average microcystin-LR concentration across the top, middle and bottom of Tank 3 at each time point.</p

Variation in microcystin detection between conventional “grab” samples and Solid Phase Adsorption Toxin Tracking (SPATT).

<p>Comparison of microcystin (MCY-LR) detection in fresh water using intermittent “grab” sampling (sample periods indicated by black circles) and SPATT (solid line indicating weekly averaged toxin values) in Pinto Lake, demonstrating the higher sensitivity of SPATT for microcystin detection. Grab samples were collected at the beginning of each weekly SPATT deployment, and from the same sample location, so each 7-day integrated SPATT deployment is bracketed by two grab samples.</p

Gross and microscopic hepatic lesions of microcystin intoxication in sea otters, compared to control livers.

<p>A.) Gross appearance of normal sea otter liver. B.) Swollen, hemorrhagic liver from a sea otter that died due to microcystin intoxication. C.) Microscopic view of normal sea otter liver, D.) Microscopic appearance of liver from an otter that died due to microcystin intoxication, demonstrating hepatocyte swelling, cytoplasmic vacuolation, necrosis or apoptosis and parenchymal hemorrhage. Small greenish-gold accumulations of bile are apparent at the upper left and center-right portions of the photomicrograph.</p