606


CAITLIN R. KEATING-BITONTI AND JONATHAN L. PAYNE Predicted maximum vol/sa (mm) low vol/sa 30 25


med. vol/sa high vol/sa


1 mm 20


15


10


5


0.0


2.5


5.0 Dissolved oxygen (ml/liter)


FIGURE 6. Contour plot showing the predicted theoretical maximum test volume–to–surface area ratio (mm) of benthic foraminifera given variations in seawater temperature and dissolved oxygen concentration under one set of physiological parameters, illustrating the fact that samples cover the full range of possible temperature and oxygen values. The observed volume–to–surface area ratios generally follow the shape of the relationship predicted from physiological first principles. The dashed line traces the saturation of dissolved oxygen in seawater. Gray open circles plot the Rotallid foraminiferal occurrences from the North American data set. Solid black shapes denote the mean seawater temperature and dissolved oxygen concentration for foraminifera that have test volume–to–surface area ratios <0.05mm (square), 0.05–0.20mm (triangle), and >0.20mm (circle). We give an example of a species from our data set with a low test volume–to–surface area ratio (Angulogerina angulosa) and one with a high test volume–to–surface area ratio (Globobulimina auriculata). The test volume–to–surface area ratios of the North American data and the theoretical maximum values show a similar trend of increasing ratios with decreasing seawater temperature and increasing dissolved oxygen concentration.


7.5


10


on spatial variation in foraminiferal morpho- logy around the North American continent, with oxygen playing a secondary role. Varia- tion in oxygen availability has been widely cited as a control on foraminiferal size evolu- tion during intervals of environmental change (Kaiho 1999b; Kaiho et al. 2006; Groves et al. 2007; Payne et al. 2011, 2012a,b; Song et al. 2011), whereas the effects of environmental temperature on metabolism and morphology appear to have been less widely appreciated. Trochospiral benthic foraminifera during the Paleocene–Eocene Thermal Maximum (PETM)


show a drastic reduction in maximumtest size across the extinction boundary that has been attributed to a decline in bottom water dissolved oxygen concentrations (Kaiho et al. 2006; Winguth et al. 2012). However, several lines of evidence suggest that warming bottom-water temperatures also played at least as important of a role. First, size decreases occurred both at sites experiencing a decline in oxygen availability (Kaiho et al. 2006) and those lacking evidence for dysoxic conditions (Alegret et al. 2010). In both cases, negative shifts in benthic isotope values across the


0.01


0.10


0.15


0.40


0.20 0.30


0.50


0.05


Temperature (°C)


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192