Maine Lobster Growth and Ocean Acidification

Anjelica Petsch GEOG 420

“Lobstering brings in about $300 million in sales a year with 5,800 licensed fishermen

who collectively haul about 3 million traps up and down the Maine coast each year.”1 The Maine

Lobster belongs to the species group American Lobster found off the Atlantic Coast of Labrador

to New Jersey, and is most colloquially known as the “Maine Labstah”. Lobster is the state of

Maine’s most lucrative fishery and is one of the most regulated fisheries in the world as Maine

has managed it for over 100 years2 and represents 75% of the state’s total commercial fishery

value3.

The area so widely known for it’s lobsters, the Gulf of Maine was created by melting of

the Laurentide Ice Sheet and is now a semi-enclosed sea that covers 36,000 square miles of

ocean. Today, the Gulf of Maine’s coastal environment includes sandy banks, rocky ledges,

deeper channels, and deep basins with water depths of over 600 feet, as well as many coastal

habitats.4

Figure 1: Screenshot of a flyover animation of the bathymetry of the Gulf of Maine created in ArcScene with the USGS DEM and contour lines made in ArcMap

1 “Maine Lobster Facts”, Get Maine Lobster, 11 Nov 2010, https://getmainelobster.com/225/maine-lobster-facts/maine-lobster-facts/, accessed 10 Dec 2017. 2 Ibid 3 Overton, Penelope, “Maine lobster catch tipped the scale at a record 130 million pounds in 2016”, Press Herald, 3 Mar 2017, http://www.pressherald.com/2017/03/03/maine-lobster-landings-set-records-in-2016/, accessed 10 Dec 2017. 4 Kennedy, Jennifer, “Gulf of Maine”, Thought Co., 17 Mar 2017, https://www.thoughtco.com/gulf-of-maine-facts-2291770, accessed 10 Dec 2017.

Figure 2: Map of the Gulf of Maine's bathymetry created by a USGS DEM file and tools to create contour lines.

The healthy marine ecosystems that house the lobster fisheries within the Gulf of Maine allowed

for a record breaking 130 million pounds of lobster valuing at $533.1 million for the year 2016;

this amount was a result of massive conservation efforts, such as a younger sexual maturity and

spawning caused from warmer waters as well as a decline of lobster’s natural predators.

Lobster’s exoskeletons are comprised of a biomineralized structure in an organic matrix,

α-chitin, and an inorganic mineral, calcium carbonate (CaCO3).5

Figure 2: Structure of biomineralized structure a-chitin compared to cellulose.6

The combination of the α-chitin and the calcium carbonate for the lobster’s exoskeleton allow

for protection and flexibility, however due to more carbon dioxide (CO2) being emitted daily and

around 22 million tons of CO2 absorbed within Earth’s oceans7, each day, the protection element

of lobster’s shell could diminish as the calcium carbonate is reacting with more acidic ocean

water. Ocean acidification is the process when water and carbon dioxide combine therefore

5 Boßelmann, F., P. Romano, H. Fabritius, D. Raabe, M. Epple, “The composition of the exoskeleton of two crustacea: The American lobster Homarus americanus and the edible crab Cancer pagurus”, ScienceDirect, 2 Aug, 2007, http://www.academia.edu/3497215/The_composition_of_the_exoskeleton_of_two_crustacea_The_American_lobster_Homarus_americanus_and_the_edible_crab_Cancer_pagurus, accessed 10 Dec 2017. 6 Jang, Mi-Kyeong, Byeong-Gi Kong, Young-Il Jeong, Change Hyung Lee, Jae-Woon Nah, “Physicochemical Characterization of α−Chitin Separated from Natural Resources”, Wiley InterScience, 5 Mar 2004, http://onlinelibrary.wiley.com/doi/10.1002/pola.20176/abstract, accessed 10 Dec 2017. 7 The Ocean Portal Team, “Ocean Acidification”, Smithsonian National Museum of Natural History, http://ocean.si.edu/ocean-acidification, accessed 10 Dec 2017.

forming carbonic acid which then binds up near by carbonate ions which are needed for

exoskeleton growth in crustaceans, such as lobsters.

In addition to excessive carbon dioxide absorbed by the world’s ocean, the Gulf of Maine

sees an increase in acidification due to phosphorous and nitrate nutrient waste runoff. The

phosphorous and nitrate waste is generated from industries, sewage, and fertilizer, as it runs into

shallow areas of the gulf, phytoplankton blooms are produced producing even more carbon

dioxide within the gulf. The shallow coastal areas of the Gulf of Maine are popular among

lobsters for reproducing as well as molting during adolescent ages.8 Typically lobster habitats are

found around 50m below the surface9 and below are images of nitrate and phosphorous levels in

the Gulf of Maine collected by NOAA’s World Ocean Atlas Select datasets. It can be seen at the

50m depth there is a higher level of both nitrate and phosphorous levels closer to the shore and

decreasing with distance. This result could be caused from the runoff produced from

neighborhood fertilizer and nearby industries that lead to harmful algal blooms, also known as

Red Tides.

8 O’Chang Studios, “A Climate Calamity In The Gulf Of Maine Part 2: Acid In The Gulf”, 9 Mar 2016, YouTube video, 4:36, https://www.youtube.com/watch?v=ZimEBFw1Q7c&feature=youtu.be, accessed 11 Dec 2017. 9 “Overview of Homarus americanus: The American Lobster”, The American Lobster, http://www.parl.ns.ca/lobster/overview.htm, accessed 12 Dec 2017.

In 2006, a collection buoy was placed in the Gulf of Maine by the PMEL’s CO2 group

and the University of New Hampshire’s Coastal Carbon Group in order to monitor the gulf’s

CO2 concentrations and seawater pH. Since the placement of the buoy, constant records are

collected and offered in graphs that depict one week, month, year, and full record options. 10

10 “GOM: Coastal Western Gulf of Maine Mooring (43.02ºN, 70.54 ºW)”, NOAA, https://www.pmel.noaa.gov/co2/story/GOM, accessed 10 Dec 2017.

The buoy’s record can be generalized in a slight decline as the water becomes more acidic which

in previous research and concern points to the gulf’s cold, fresh water allowing for it’s sensitivity

to ocean acidification.11

Using the data from the Ocean Climate Change lab, the maps below were created by

using the map algebra tool to create a formula subtracting the baseline values from the 2050

layer’s values of nitrate, phosphorous and pH. After calculating the change of nitrate level

between baseline and year 2050, it can be seen in the nitrate map that further from the shore will

show a moderate change of around 0.014. As for the change in phosphorous levels the dataset

used showed a very low, -0.000189, change in phosphorous amounts. Although the results for

change in nitrate and phosphorous levels seem low or moderate, the change ever so slightly can

disrupt the Gulf of Maine’s ecosystem by eliminating a species either by migration or death.

Despite the Gulf of Maine also showing a limited decline trend in pH, between -0.289278 and

-0.127419, shown both in the map below between today and 2050 and the graph created by the

Gulf of Maine Buoy in 2006, the pH scale is created logarithmically and going from the area’s

normal pH 8 to 7 is adding 10 times more acid to the area’s water12.

11 “Ocean Acidification: A Growing Concern in the Gulf of Maine”, Gulf of Main Research Institute, 28 May 2014, https://www.gmri.org/news/waypoints/ocean-acidification-growing-concern-gulf-maine, accessed 10 Dec 2017. 12 See note 6.

Figure 3: Map created in ArcMaps using map algebra tool to find the change in pH between 2000-2050 within the surface area of the Gulf of Maine.

With today’s enormous levels of carbon dioxide being spewed into the atmosphere and

absorbed by seawater, and the phosphorous and nitrate nutrient runoff from near by industries,

fertilizer from neighborhoods, and sewage all deplete the the natural buffering abilities of the

oceans as the natural basic chemical characteristics can not balance the CO2 levels quick enough.

The cold water of the Gulf of Maine allows for continuous growth in the lobster fisheries

business, but can also result in delaying the hard-shell lobsters from returning closer to the shore

to molt13 as well as aiding to the sensitivity of ocean acidification which could also result in

overall weaker shells and higher mortality rates within lobster populations.

13 Overton, Penelope, “First half of Maine’s lobstering season ‘painfully slow’ for fishermen”, 4 Oct 2017, http://www.pressherald.com/2017/10/04/first-half-of-maines-lobstering-season-painfully-slow-for-fishermen/, accessed 10 Dec 2017.

Bibliography

Boßelmann, F., P. Romano, H. Fabritius, D. Raabe, M. Epple, “The composition of the exoskeleton of two crustacea: The American lobster Homarus americanus and the edible crab Cancer pagurus”, ScienceDirect, 2 Aug, 2007, http://www.academia.edu/3497215/The_composition_of_the_exoskeleton_of_two_crustacea_The_American_lobster_Homarus_americanus_and_the_edible_crab_Cancer_pagurus, accessed 10 Dec 2017.

“GOM: Coastal Western Gulf of Maine Mooring (43.02ºN, 70.54 ºW)”, NOAA,

https://www.pmel.noaa.gov/co2/story/GOM, accessed 10 Dec 2017. Jang, Mi-Kyeong, Byeong-Gi Kong, Young-Il Jeong, Change Hyung Lee, Jae-Woon Nah,

“Physicochemical Characterization of α−Chitin Separated from Natural Resources”, Wiley InterScience, 5 Mar 2004, http://onlinelibrary.wiley.com/doi/10.1002/pola.20176/abstract, accessed 10 Dec 2017.

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“Overview of Homarus americanus: The American Lobster”, The American Lobster, http://www.parl.ns.ca/lobster/overview.htm, accessed 12 Dec 2017.

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